View source for Interval (music)

{{Short description|Difference in pitch between two notes}}
{{For|albums or bands named Intervals|Interval (disambiguation)}}
{{Use dmy dates|date=April 2017}}
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d,1 g f \bar "||" \break
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|caption=Melodic and harmonic intervals
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In [[music theory]], an '''interval''' is a difference in [[pitch (music)|pitch]] between two sounds.<ref>{{Citation | last = Prout | first = Ebenezer|author-link=Ebenezer Prout| title=Harmony, Its Theory and Practice | publisher = London: Augener; Boston: Boston Music Co. | edition = 30th edition, revised and largely rewritten | year = 1903 | chapter = I-Introduction | page = 1 | isbn = 978-0781207836}}</ref> An interval may be described as '''horizontal''', '''linear''', or '''melodic''' if it refers to successively sounding tones, such as two adjacent pitches in a melody, and '''vertical''' or '''harmonic''' if it pertains to simultaneously sounding tones, such as in a [[Chord (music)|chord]].<ref name="LindleyMarkCampbell">{{Cite Grove |last1=Lindley |first1=Mark |last2=Campbell |first2=Murray |last3=Greated |first3=Clive |title=Interval}}</ref><ref>{{Citation|last1 = Aldwell | first1 = E.| last2 = Schachter | first2 = C. | last3 = Cadwallader | first3 = A. |title = Harmony and Voice Leading | edition = 4th | chapter = Part 1: The Primary Materials and Procedures, Unit 1 | date = 11 March 2010 | page = 8 | publisher = Schirmer | isbn = 978-0495189756}}</ref>

In [[Western culture|Western]] music, intervals are most commonly differences between [[musical note|notes]] of a [[diatonic scale]]. Intervals between successive notes of a scale are also known as scale steps. The smallest of these intervals is a [[semitone]]. Intervals smaller than a semitone are called [[microtone]]s. They can be formed using the notes of various kinds of non-diatonic scales. Some of the very smallest ones are called [[Comma (music)|commas]], and describe small discrepancies, observed in some [[tuning system]]s, between [[enharmonic|enharmonically equivalent]] notes such as C{{music|#}} and D{{music|flat}}. Intervals can be arbitrarily small, and even imperceptible to the human ear.

In physical terms, an interval is the [[Interval ratio|ratio]] between two sonic frequencies. For example, any two notes an octave apart have a frequency ratio of 2:1. This means that successive increments of pitch by the same interval result in an exponential increase of frequency, even though the human ear perceives this as a linear increase in pitch. For this reason, intervals are often measured in [[Cent (music)|cents]], a unit derived from the [[logarithm]] of the frequency ratio.

In Western music theory, the most common naming scheme for intervals describes two properties of the interval: the [[#Quality|quality]] (perfect, major, minor, augmented, diminished) and [[#Number|number]] (unison, second, third, etc.). Examples include the [[minor third]] or [[perfect fifth]]. These names identify not only the difference in semitones between the upper and lower notes but also how the interval is [[enharmonic spelling|spelled]]. The importance of spelling stems from the historical practice of differentiating the frequency ratios of enharmonic intervals such as G–G{{music|#}} and G–A{{music|b}}.<ref>{{Citation | last = Duffin | first = Ross W. | title=How Equal Temperament Ruined Harmony (and Why You Should Care) | publisher = W. W. Norton | edition = 1st | year = 2007 | chapter = 3. Non-keyboard tuning | isbn = 978-0-393-33420-3}}</ref>

== Size ==
{{Image frame|content=<score sound="1">
\relative c'{
\hide Staff.TimeSignature
<d f>1 | d4 f d2
}
</score>
|width=300|caption=Example: Minor third on D in equal temperament: 300 cents.
}}

The size of an interval (also known as its width or height) can be represented using two alternative and equivalently valid methods, each appropriate to a different context: frequency ratios or cents.

=== Frequency ratios ===
{{Main|Interval ratio}}

The size of an interval between two notes may be measured by the [[ratio]] of their [[frequency|frequencies]]. When a [[musical instrument]] is tuned using a [[just intonation]] tuning system, the size of the main intervals can be expressed by small-[[Integer number|integer]] ratios, such as 1:1 ([[unison]]), 2:1 ([[octave]]), 5:3 ([[major sixth]]), 3:2 ([[perfect fifth]]), 4:3 ([[perfect fourth]]), 5:4 ([[major third]]), 6:5 ([[minor third]]). Intervals with small-integer ratios are often called ''just intervals'', or ''pure intervals''.

Most commonly, however, musical instruments are nowadays tuned using a different tuning system, called [[12-tone equal temperament]]. As a consequence, the size of most equal-tempered intervals cannot be expressed by small-integer ratios, although it is very close to the size of the corresponding just intervals. For instance, an [[equal temperament|equal-tempered]] fifth has a frequency ratio of 2{{sup|{{frac|7|12}}}}:1, approximately equal to 1.498:1, or 2.997:2 (very close to 3:2). For a comparison between the size of intervals in different tuning systems, see {{Section link||Size of intervals used in different tuning systems}}.

=== Cents ===
{{Main|Cent (music)}}

The standard system for comparing interval sizes is with [[Cent (music)|cents]]. The cent is a [[logarithmic scale|logarithmic]] unit of measurement. If frequency is expressed in a [[logarithmic scale]], and along that scale the distance between a given frequency and its double (also called [[octave]]) is divided into 1200 equal parts, each of these parts is one cent. In twelve-tone [[equal temperament]] (12-TET), a tuning system in which all [[semitone]]s have the same size, the size of one semitone is exactly 100 cents. Hence, in 12-TET the cent can be also defined as one hundredth of a [[semitone]].

Mathematically, the size in cents of the interval from frequency ''f''<sub>1</sub> to frequency ''f''<sub>2</sub> is

<math display="block">n = 1200 \cdot \log_2 \left( \frac{f_2}{f_1} \right)</math>

== Main intervals ==
<!--This section is linked from [[List of pitch intervals]] ([[MOS:HEAD]])-->

The table shows the most widely used conventional names for the intervals between the notes of a [[chromatic scale]]. A [[perfect unison]] (also known as perfect prime)<ref name=prime>[http://www.oxfordmusiconline.com/subscriber/article/grove/music/53859 "Prime (ii). See Unison"], ''[[Grove Music Online]]''. Oxford University Press. Accessed August 2013. {{subscription required}})</ref> is an interval formed by two identical notes. Its size is zero [[Cent (music)|cents]]. A [[semitone]] is any interval between two adjacent notes in a chromatic scale, a [[whole tone]] is an interval spanning two semitones (for example, a [[major second]]), and a [[tritone]] is an interval spanning three tones, or six semitones (for example, an augmented fourth).{{efn|name=TritoneA4|The term [[tritone]] is sometimes used more strictly as a synonym of augmented fourth (A4).}} Rarely, the term [[ditone]] is also used to indicate an interval spanning two whole tones (for example, a [[major third]]), or more strictly as a synonym of major third.

Intervals with different names may span the same number of semitones, and may even have the same width. For instance, the interval from D to F{{Music|#}} is a [[major third]], while that from D to G{{Music|b}} is a [[diminished fourth]]. However, they both span 4 semitones. If the [[Musical instrument|instrument]] is tuned so that the 12 notes of the chromatic scale are equally spaced (as in [[equal temperament]]), these intervals also have the same width. Namely, all semitones have a width of 100 [[Cent (music)|cents]], and all intervals spanning 4 semitones are 400 cents wide.

The names listed here cannot be determined by counting semitones alone. The rules to determine them are explained below. Other names, determined with different naming conventions, are listed in [[#Alternative interval naming conventions|a separate section]]. Intervals [[#Minute intervals|smaller than one semitone]] (commas or microtones) and [[#Compound intervals|larger than one octave]] (compound intervals) are introduced below.

{|class="wikitable"
|-
! Number of<br/>[[semitone]]s|| [[#Quality|Minor, major,<br/>or perfect]] intervals || Short || [[#Quality|Augmented or<br/>diminished]] intervals || Short || Widely used<br/>[[#Alternative interval naming conventions|alternative names]] || Short || Audio
|-
| 0 || [[Perfect unison]] || P1 || [[Diminished second]] || d2 || || || {{audio|Unison on C.mid|Play}}
|-
| 1 || [[Minor second]] || m2 || [[Augmented unison]] || A1 || [[Semitone]], half tone, half step || S || {{audio|Minor second on C.mid|Play}}
|-
| 2 || [[Major second]] || M2 || [[Diminished third]] || d3 || [[Whole tone|Tone]], whole tone, whole step || T || {{audio|Major second on C.mid|Play}}
|-
| 3 || [[Minor third]] || m3 || [[Augmented second]] || A2 || || || {{audio|Minor third on C.mid|Play}}
|-
| 4 || [[Major third]] || M3 || [[Diminished fourth]] || d4 || || || {{audio|Major third on C.mid|Play}}
|-
| 5 || [[Perfect fourth]] || P4 || [[Augmented third]] || A3 || || || {{audio|Perfect fourth on C.mid|Play}}
|-
| rowspan="2"| 6 || rowspan="2" colspan="2"| || [[Tritone|Diminished fifth]] || d5 || rowspan="2"|[[Tritone]] || rowspan="2"| TT || rowspan="2"| {{audio|Tritone on C.mid|Play}}
|-
| [[Tritone|Augmented fourth]] || A4
|-
| 7 || [[Perfect fifth]] || P5 || [[Diminished sixth]] || d6 || || || {{audio|Perfect fifth on C.mid|Play}}
|-
| 8 || [[Minor sixth]] || m6 || [[Augmented fifth]] || A5 || || || {{audio|Minor sixth on C.mid|Play}}
|-
| 9 || [[Major sixth]] || M6 || [[Diminished seventh]] || d7 || || || {{audio|Major sixth on C.mid|Play}}
|-
| 10 || [[Minor seventh]] || m7 || [[Augmented sixth]] || A6 || || || {{audio|Minor seventh on C.mid|Play}}
|-
| 11 || [[Major seventh]] || M7 || [[Diminished octave]] || d8 || || || {{audio|Major seventh on C.mid|Play}}
|-
| 12 || [[Octave|Perfect octave]] || P8 || [[Augmented seventh]] || A7 || || || {{audio|Perfect octave on C.mid|Play}}
|}

== Interval number and quality ==
[[File:Main intervals from C.png|thumb|450px|right|Main intervals from C[[File:Intervals.mid]]]]

In Western [[music theory]], an interval is named according to its ''number'' (also called ''diatonic number, interval size''<ref>{{Cite book |last=Burstein |first=L. Poundie |title=Concise Introduction to Tonal Harmony |last2=Straus |first2=Joseph N. |publisher=W. W. Norton |year=2016 |isbn=978-0-393-26476-0 |edition=1st |location=New York |pages=55}}</ref> or ''generic interval''<ref name=":0">{{Cite book |last=Laitz |first=Steven G. |title=The Complete Musician: An Integrated Approach to Theory, Analysis, and Listening |publisher=[[Oxford University Press]] |year=2016 |isbn=9780199347094 |edition=4th |location=New York |pages=27–31}}</ref>) and ''quality''. For instance, ''major third'' (or '''M3''') is an interval name, in which the term ''major'' ('''M''') describes the quality of the interval, and ''third'' ('''3''') indicates its number.

=== Number ===
<!--[[Major second]] links directly here-->
[[Image:Staff lines and spaces SVG.svg|right|thumb|350px|[[Staff (music)|Staff]], with [[staff position]]s indicated]]
[[Image:Fifth C to G.png|right|thumb|Fifth from C to G in the A{{music|b}} [[major scale]]]]

The number of an interval is the number of letter names or [[staff position]]s (lines and spaces) it encompasses, including the positions of both notes forming the interval. For instance, the interval B—D is a third (denoted '''m3''') because the notes from B to the D above it encompass three letter names (B, C, D) and occupy three consecutive staff positions, including the positions of B and D. The [[#Main intervals|table]] and the figure above show intervals with numbers ranging from 1 (e.g., '''P1''') to 8 (e.g., '''d8'''). Intervals with larger numbers are called [[#Compound intervals|compound intervals]].

There is a [[one-to-one correspondence]] between staff positions and diatonic-scale [[Degree (music)|degrees]] (the notes of [[diatonic scale]]).{{efn|name=diatonic|
The expression [[diatonic scale]] is herein strictly defined as a [[Heptatonic scale|7-tone scale]], which is either a sequence of successive [[natural note]]s (such as the C-[[major scale]], C–D–E–F–G–A–B, or the A-[[minor scale]], A–B–C–D–E–F–G) or any [[transposition (music)|transposition]] thereof. In other words, a scale that can be written using seven consecutive notes without [[Accidental (music)|accidentals]] on a [[Staff (music)|staff]] with a conventional [[key signature]], or with no signature. This includes, for instance, the [[Major scale|major]] and the [[Natural minor scale|natural minor]] scales, but does not include some other seven-tone scales, such as the [[Melodic minor scale|melodic minor]] and the [[Harmonic minor scale|harmonic minor]] scales (see also [[Diatonic and chromatic]]).}}
This means that interval numbers can also be determined by counting diatonic scale degrees, rather than staff positions, provided that the two notes that form the interval are drawn from a diatonic scale. Namely, B—D is a third because in any diatonic scale that contains B and D, the sequence from B to D includes three notes. For instance, in the B-[[natural minor scale|natural minor]] diatonic scale, the three notes are B–C{{music|sharp}}–D. This is not true for all kinds of scales. For instance, in a [[chromatic scale]], there are four notes from B to D: B–C–C{{music|sharp}}–D. This is the reason interval numbers are also called ''diatonic numbers'', and this convention is called ''diatonic numbering''.

If one adds any [[accidental (music)|accidental]]s to the notes that form an interval, by definition the notes do not change their staff positions. As a consequence, any interval has the same interval number as the corresponding [[Natural (music)|natural]] interval, formed by the same notes without accidentals. For instance, the intervals B–D{{music|sharp}} (spanning 4 semitones) and B–D{{music|flat}} (spanning 2 semitones) are thirds, like the corresponding natural interval B—D (3 semitones).

Notice that interval numbers represent an inclusive count of encompassed staff positions or note names, not the difference between the endpoints. In other words, one starts counting the lower pitch as one, not zero. For that reason, the interval E–E, a perfect unison, is also called a prime (meaning "1"), even though there is no difference between the endpoints. Continuing, the interval E–F{{music|sharp}} is a second, but F{{music|sharp}} is only one staff position, or diatonic-scale degree, above E. Similarly, E—G{{music|sharp}} is a third, but G{{music|sharp}} is only two staff positions above E, and so on. As a consequence, joining two intervals always yields an interval number one less than their sum. For instance, the intervals B—D and D—F{{music|sharp}} are thirds, but joined together they form a fifth (B—F{{music|sharp}}), not a sixth. Similarly, a stack of three thirds, such as B—D, D—F{{music|sharp}}, and F{{music|sharp}}—A, is a seventh (B-A), not a ninth.

This scheme applies to intervals up to an octave (12 semitones). For larger intervals, see {{format link|#Compound intervals}} below.

=== Quality <span class="anchor" id="major_minor_perfect_anchor"></span>===
[[File:diatonic intervals.png|right|frame|Intervals formed by the notes of a C major [[diatonic scale]]]]

The name of any interval is further qualified using the terms '''perfect''' ('''P'''), [[Major and minor|major]] ('''M'''), [[Major and minor|minor]] ('''m'''), [[Augmentation (music)|augmented]] ('''A'''), and [[Diminution|diminished]] ('''d'''). This is called its ''interval quality'' (or ''modifier''<ref name=":1">{{Cite book |last=Kostka |first=Stefan |title=Tonal Harmony, with an Introduction to Post-Tonal Music |last2=Payne |first2=Dorothy |last3=Almén |first3=Byron |publisher=[[McGraw Hill]] |year=2018 |isbn=9781259447099 |edition=8th |location=New York |pages=16–18}}</ref><ref name=":0" />). It is possible to have doubly diminished and doubly augmented intervals, but these are quite rare, as they occur only in [[chromatic]] contexts. The combination of number (or generic interval) and quality (or modifier) is called the ''specific interval'',<ref name=":0" /> ''diatonic interval'' (sometimes used only for intervals appearing in the diatonic scale), or simply ''interval''.<ref name=":1" />

The quality of a [[#Compound intervals|compound interval]] is the quality of the simple interval on which it is based. Some other qualifiers like ''neutral'', ''subminor'', and ''supermajor'' are used for [[#Non-diatonic intervals|non-diatonic intervals]].

==== Perfect ====
[[Image:Perfect intervals on C.png|thumb|Perfect intervals on C: {{audio|Unison on C.mid|PU}}, {{audio|Perfect fourth on C.mid|P4}}, {{audio|Perfect fifth on C.mid|P5}}, {{audio|Perfect octave on C.mid|P8}}]]
Perfect intervals are so-called because they were traditionally considered perfectly consonant,<ref name=Weber>
Definition of ''perfect consonance'' from
{{cite book |url=https://archive.org/details/bub_gb_20oBAAAAYAAJ |quote=perfect concord |first=Godfrey |last=Weber |title=General Music Teacher |year=1841}}
</ref>
although in Western classical music the perfect fourth was sometimes regarded as a less than perfect consonance, when its function was [[Counterpoint|contrapuntal]].{{Vague|date=February 2013}} Conversely, minor, major, augmented, or diminished intervals are typically considered less consonant, and were traditionally classified as mediocre consonances, imperfect consonances, or near-dissonances.<ref name=Weber/>

Within a [[diatonic scale]]{{efn|name=diatonic}} all unisons ('''P1''') and octaves ('''P8''') are perfect. Most fourths and fifths are also perfect ('''P4''' and '''P5'''), with five and seven semitones respectively. One occurrence of a fourth is augmented ('''A4''') and one fifth is diminished ('''d5'''), both spanning six semitones. For instance, in an E-major scale, the '''A4''' is between A and D{{music|sharp}}, and the '''d5''' is between D{{music|sharp}} and A.

The [[Inversion (music)#Intervals|inversion]] of a perfect interval is also perfect. Since the inversion does not change the [[pitch class]] of the two notes, it hardly affects their level of consonance (matching of their [[Harmonic series (music)|harmonics]]). Conversely, other kinds of intervals have the opposite quality with respect to their inversion. The inversion of a major interval is a minor interval, and the inversion of an augmented interval is a diminished interval.

==== Major and minor ====
[[Image:Major and minor intervals on C.png|thumb|Major and minor intervals on C: {{audio|Minor second on C.mid|m2}}, {{audio|Major second on C.mid|M2}}, {{audio|Minor third on C.mid|m3}}, {{audio|Major third on C.mid|M3}}, {{audio|Minor sixth on C.mid|m6}}, {{audio|Dim seventh on C.mid|M6}}, {{audio|Minor seventh on C.mid|m7}}, {{audio|Major seventh on C.mid|M7}}]]
As shown in the table, a [[diatonic scale]]{{efn|name=diatonic}} defines seven intervals for each interval number, each starting from a different note (seven unisons, seven seconds, etc.). The intervals formed by the notes of a diatonic scale are called diatonic. Except for unisons and octaves, the diatonic intervals with a given interval number always occur in two sizes, which differ by one semitone. For example, six of the fifths span seven semitones. The other one spans six semitones. Four of the thirds span three semitones, the others four. If one of the two versions is a perfect interval, the other is called either diminished (i.e. narrowed by one semitone) or augmented (i.e. widened by one semitone). Otherwise, the larger version is called major, the smaller one minor. For instance, since a 7-semitone fifth is a perfect interval ('''P5'''), the 6-semitone fifth is called "diminished fifth" ('''d5'''). Conversely, since neither kind of third is perfect, the larger one is called "major third" ('''M3'''), the smaller one "minor third" ('''m3''').

Within a diatonic scale,{{efn|name=diatonic}} unisons and octaves are always qualified as perfect, fourths as either perfect or augmented, fifths as perfect or diminished, and all the other intervals (seconds, thirds, sixths, sevenths) as major or minor.

==== Augmented and diminished ====
{{further|Augmented interval|Diminished interval}}
[[Image:Augmented and diminished intervals on C.png|thumb|300px|Augmented and diminished intervals on C: {{audio|Unison on C.mid|d2}}, {{audio|Minor third on C.mid|A2}}, {{audio|Major second on C.mid|d3}}, {{audio|Perfect fourth on C.mid|A3}}, {{audio|Major third on C.mid|d4}}, {{audio|Tritone on C.mid|A4}}, {{audio|Tritone on C.mid|d5}}, {{audio|Minor sixth on C.mid|A5}}, {{audio|Perfect fifth on C.mid|d6}}, {{audio|Minor seventh on C.mid|A6}}, {{audio|Dim seventh on C.mid|d7}}, {{audio|Perfect octave on C.mid|A7}}, {{audio|Major seventh on C.mid|d8}}, {{audio|Minor ninth on C.mid|A8}}]]
Augmented intervals are wider by one semitone than perfect or major intervals, while having the same interval number (i.e., encompassing the same number of staff positions): they are wider by a [[chromatic semitone]]. Diminished intervals, on the other hand, are narrower by one semitone than perfect or minor intervals of the same interval number: they are narrower by a chromatic semitone. For instance, an augmented sixth such as E{{music|flat}}–C{{music|sharp}} spans ten semitones, exceeding a major sixth (E{{music|flat}}—C) by one semitone, while a diminished sixth such as E{{music|sharp}}–C spans seven semitones, falling short of a minor sixth (E{{music|sharp}}–C{{music|sharp}}) by one semitone.

The augmented fourth ('''A4''') and the diminished fifth ('''d5''') are the only augmented and diminished intervals that appear in diatonic scales{{efn|name=diatonic}} (see table).

=== Example ===
Neither the number, nor the quality of an interval can be determined by counting [[semitones]] alone. As explained above, the number of staff positions must be taken into account as well.

For example, as shown in the table below, there are six semitones between C and F{{music|sharp}}, C and G{{music|flat}}, and C{{music|flat}} and E{{music|sharp}}, but
* C–F{{music|sharp}} is a fourth, as it encompasses four staff positions (C, D, E, F), and it is augmented, as it exceeds a perfect fourth (such as C-F) by one semitone.
* C–G{{music|flat}} is a fifth, as it encompasses five staff positions (C, D, E, F, G), and it is diminished, as it falls short of a perfect fifth (such as C-G) by one semitone.
* C{{music|flat}}–E{{music|sharp}} is a third, as it encompasses three staff positions (C, D, E), and it is doubly augmented, as it exceeds a major third (such as C-E) by two semitone.

{|class="wikitable"
! rowspan="2" ; style="text-align: left" | Number<br/>of semitones || rowspan="2" ; style="text-align: left" | Interval name || colspan="5"| [[Staff position]]s
|-
! 1 || 2 || 3 || 4 || 5
|-
| 6 || [[augmented fourth]] ('''A4''') || C || &nbsp; || &nbsp; || F{{music|sharp}} ||
|-
| 6 || [[diminished fifth]] ('''d5''') || C || &nbsp; || &nbsp; || &nbsp; || G{{music|flat}}
|-
| 6 || doubly [[augmented third]] ('''AA3''') || C{{music|flat}} || &nbsp; || E{{music|sharp}} || &nbsp; ||
|}

== Shorthand notation ==
Intervals are often abbreviated with a '''P''' for perfect, '''m''' for [[Major and minor|minor]], '''M''' for [[Major and minor|major]], '''d''' for [[Diminution|diminished]], '''A''' for [[Augmentation (music)|augmented]], followed by the interval number. The indications M and P are often omitted. The [[octave]] is P8, and a [[unison]] is usually referred to simply as "a unison" but can be labeled P1. The [[tritone]], an augmented fourth or diminished fifth is often '''TT'''. The interval qualities may be also abbreviated with '''perf''', '''min''', '''maj''', '''dim''', '''aug'''. Examples:
* m2 (or min2): minor second,
* M3 (or maj3): major third,
* A4 (or aug4): augmented fourth,
* d5 (or dim5): diminished fifth,
* P5 (or perf5): perfect fifth.

== Inversion ==
{{Main|Inversion (music)#Intervals}}
[[Image:Compound interval inversion.png|thumb|350px|Major 13th (compound major 6th) inverts to a minor 3rd by moving the bottom note up two octaves, the top note down two octaves, or both notes one octave.]]

A simple interval (i.e., an interval smaller than or equal to an octave) may be [[inversion (music)|inverted]] by raising the lower pitch an [[octave]] or lowering the upper pitch an octave. For example, the fourth from a lower C to a higher F may be inverted to make a fifth, from a lower F to a higher C.

: <score sound="1">
{
\override Score.TimeSignature
#'stencil = ##f
\override Score.SpacingSpanner.strict-note-spacing = ##t
\set Score.proportionalNotationDuration = #(ly:make-moment 1/4)
\new Staff <<
   \clef treble \time 4/4
   \new Voice \relative c' {
      \stemUp c2 c' c, c' c, c' c, c'
      } 
   \new Voice \relative c' {
      \stemDown c2 c d d e e f f
      }
   \addlyrics { "P1" -- "P8" "M2" -- "m7" "M3" -- "m6" "P4" -- "P5" }
>>
}
</score>

There are two rules to determine the number and quality of the inversion of any simple interval:<ref>[[Stefan Kostka|Kostka, Stefan]]; Payne, Dorothy (2008). ''Tonal Harmony'', p.&nbsp;21. First edition, 1984.</ref>
# The interval number and the number of its inversion always add up to nine (4 + 5 = 9, in the example just given).
# The inversion of a major interval is a minor interval, and vice versa; the inversion of a perfect interval is also perfect; the inversion of an augmented interval is a diminished interval, and vice versa; the inversion of a doubly augmented interval is a doubly diminished interval, and vice versa.
For example, the interval from C to the E{{Music|b}} above it is a minor third. By the two rules just given, the interval from E{{Music|b}} to the C above it must be a major sixth.

Since compound intervals are larger than an octave, "the inversion of any compound interval is always the same as the inversion of the simple interval from which it is compounded".<ref>[[Ebenezer Prout|Prout, Ebenezer]] (1903). ''Harmony: Its Theory and Practice'', 16th edition. London: Augener & Co. (facsimile reprint, St. Clair Shores, Michigan: Scholarly Press, 1970), p.&nbsp;10. {{ISBN|0-403-00326-1}}.</ref>

For intervals identified by their ratio, the inversion is determined by reversing the ratio and multiplying the ratio by 2 until it is greater than 1. For example, the inversion of a 5:4 ratio is an 8:5 ratio.

For intervals identified by an integer number of semitones, the inversion is obtained by subtracting that number from 12.

Since an [[interval class]] is the lower number selected among the interval integer and its inversion, interval classes cannot be inverted.

== Classification ==
Intervals can be described, classified, or compared with each other according to various criteria.

{{Image frame|content=<score sound="1" override_midi="Melodic and harmonic intervals.mid">
\layout {
line-width = 60\mm
indent = 0\mm
}
\relative c''{
\clef treble \time 3/1 \hide Staff.TimeSignature
d,1 g f \bar "||" \break
\time 1/1 <d f> \bar "||" <d g> \bar "||" <f g> \bar "||"
}
</score>
|caption=Melodic and harmonic intervals
}}

=== Melodic and harmonic ===<!--[[Melodic interval]] and [[harmonic interval]] redirect directly here.-->
{{Main|Harmony|Melody}}
An interval can be described as
* Vertical or [[harmony|harmonic]] if the two notes sound simultaneously
* Horizontal, linear, or [[melody|melodic]] if they sound successively.<ref name="LindleyMarkCampbell" /> Melodic intervals can be ''ascending'' (lower pitch precedes higher pitch) or ''descending''.

=== Diatonic and chromatic ===
{{Main|Diatonic and chromatic}}
In general,

* A ''[[diatonic]] interval'' is an interval formed by two notes of a [[diatonic scale]].
* A ''chromatic interval'' is a non-diatonic interval formed by two notes of a [[chromatic scale]].

[[File:Chromatic scale full octave ascending and descending on C.PNG|thumb|500px|Ascending and descending chromatic scale on C[[File:ChromaticScaleUpDown.ogg]]]]

The table [[#Quality|above]] depicts the 56 diatonic intervals formed by the notes of the C major scale (a diatonic scale). Notice that these intervals, as well as any other diatonic interval, can be also formed by the notes of a chromatic scale.

The distinction between diatonic and chromatic intervals is controversial, as it is based on the definition of diatonic scale, which is variable in the literature. For example, the interval B–E{{music|flat}} (a [[diminished fourth]], occurring in the [[Harmonic minor scale|harmonic C-minor scale]]) is considered diatonic if the harmonic minor scales are considered diatonic as well.<ref>See for example William Lovelock, ''The Rudiments of Music'' (New York: St Martin's Press; London: G. Bell, 1957): {{Page needed|date=August 2015}}, reprinted 1966, 1970, and 1976 by G. Bell, 1971 by St Martins Press, 1981, 1984, and 1986 London: Bell & Hyman. {{ISBN|9780713507447}} (pbk). {{ISBN|9781873497203}}</ref> Otherwise, it is considered chromatic. For further details, see the [[Diatonic and chromatic|main article]].

By a commonly used definition of diatonic scale{{efn|name=diatonic}} (which excludes the [[harmonic minor]] and [[melodic minor]] scales), all perfect, major and minor intervals are diatonic. Conversely, no augmented or diminished interval is diatonic, except for the augmented fourth and diminished fifth.

[[File:Ab major scale.png|right|thumb|[[A-flat major|A{{music|b}}-major]] scale[[File:Ab major scale.mid]]]]

The distinction between diatonic and chromatic intervals may be also sensitive to context. The above-mentioned 56 intervals formed by the C-major scale are sometimes called ''diatonic to C major''. All other intervals are called ''chromatic to C major''. For instance, the perfect fifth A{{Music|flat}}–E{{Music|flat}} is chromatic to C major, because A{{Music|flat}} and E{{Music|flat}} are not contained in the C major scale. However, it is diatonic to others, such as the A{{Music|flat}} major scale.

=== Consonant and dissonant ===<!--[[Interval strength]] redirects directly here-->
{{Main|Consonance and dissonance}}
[[Consonance and dissonance]] are relative terms that refer to the stability, or state of repose, of particular musical effects. Dissonant intervals are those that cause tension and desire to be ''resolved'' to consonant intervals.

These terms are relative to the usage of different compositional styles.
* In [[Renaissance music|15th- and 16th-century]] usage, perfect fifths and octaves, and major and minor thirds and sixths were considered harmonically consonant, and all other intervals dissonant, including the perfect fourth, which by 1473 was described (by [[Johannes Tinctoris]]) as dissonant, except between the upper parts of a vertical sonority—for example, with a supporting third below ("6-3 chords").<ref>Drabkin, William (2001). "Fourth". ''[[The New Grove Dictionary of Music and Musicians]]'', second edition, edited by [[Stanley Sadie]] and [[John Tyrrell (musicologist)|John Tyrrell]]. London: Macmillan.</ref> In the [[common practice period]], it makes more sense to speak of consonant and dissonant chords, and certain intervals previously considered dissonant (such as minor sevenths) became acceptable in certain contexts. However, 16th-century practice was still taught to beginning musicians throughout this period.
* [[Hermann von Helmholtz]] (1821–1894) theorised that dissonance was caused by the presence of [[beat (acoustics)|beats]].{{sfn|Helmholtz|1895|loc=p. 172: "The roughness from sounding two tones together depends... the number of beats produced in a second."}} Helmholtz further believed that the beating produced by the upper partials of harmonic sounds was the cause of dissonance for intervals too far apart to produce beating between the [[Fundamental frequency|fundamentals]].{{sfn|Helmholtz|1895|loc=p. 178: "The cause of this phenomenon must be looked for in the beats produced by the high upper partials of such compound tones"}} Helmholtz then designated that two harmonic tones that shared common low partials would be more consonant, as they produced less beats.{{sfn|Helmholtz|1895|p=182}}<ref>[[Hermann von Helmholtz|Helmholtz, Hermann L. F.]] ''[[Sensations of Tone|On the Sensations of Tone as a Theoretical Basis for the Theory of Music]]'', 2nd English edition, translated by [[Alexander John Ellis|Ellis, Alexander J.]] (1885) reprinted by Dover Publications with new introduction (1954) {{ISBN|0-486-60753-4}}, p. 182d: "Just as the coincidences of the two first upper partial tones led us to the natural consonances of the Octave and Fifth, the coincidences of higher upper partials would lead us to a further series of natural consonances."</ref> Helmholtz disregarded partials above the seventh, as he believed that they were not audible enough to have significant effect.{{sfn|Helmholtz|1895|loc=p. 183: "Here I have stopped, because the 7th partial tone is entirely eliminated, or at least much weakened."}} From this Helmholtz categorises the octave, perfect fifth, perfect fourth, major sixth, major third, and minor third as consonant, in decreasing value, and other intervals as dissonant.
* [[David Cope]] (1997) suggests the concept of '''interval strength''',<ref name="Cope">[[David Cope|Cope, David]] (1997). ''Techniques of the Contemporary Composer'', pp.&nbsp;40–41. New York, New York: Schirmer Books. {{ISBN|0-02-864737-8}}.</ref> in which an interval's strength, consonance, or stability is determined by its approximation to a lower and stronger, or higher and weaker, position in the [[harmonic series (music)|harmonic series]]. See also: [[Lipps–Meyer law]] and [[#Interval root]]

All of the above analyses refer to vertical (simultaneous) intervals.

=== Simple and compound ===
[[File:Simple and compound major third.png|thumb|Simple and compound major third[[File:Simple and compound major third.mid]]]]

A simple interval is an interval spanning at most one octave (see [[#Main intervals|Main intervals]] above). Intervals spanning more than one octave are called compound intervals, as they can be obtained by adding one or more octaves to a simple interval (see [[#Compound intervals|below]] for details).<ref name="compound">{{cite book
  | last1=Wyatt|first=Keith|author1-link=Keith Wyatt|last2=Schroeder|first2=Carl|author2-link=Carl Schroeder (pianist)|title=Harmony & Theory
  | publisher = [[Hal Leonard Corporation]]
  | year = 1998
  | page = 77
  | isbn = 9780793579914}}</ref>

=== Steps and skips ===
{{Main|Steps and skips}}
Linear (melodic) intervals may be described as ''steps'' or ''skips''. A ''step'', or ''conjunct motion'',<ref name=Bonds>
Bonds, Mark Evan (2006).
''A History of Music in Western Culture'', p.123. 2nd ed. {{ISBN|0-13-193104-0}}.</ref>
is a linear interval between two consecutive notes of a scale. Any larger interval is called a ''skip'' (also called a ''leap''), or ''disjunct motion''.<ref name="Bonds"/> In the [[diatonic scale]],{{efn|name=diatonic}} a step is either a [[minor second]] (sometimes also called ''half step'') or [[major second]] (sometimes also called ''whole step''), with all intervals of a [[minor third]] or larger being skips.

For example, C to D (major second) is a step, whereas C to E ([[major third]]) is a skip.

More generally, a step is a smaller or narrower interval in a musical line, and a skip is a wider or larger interval, where the categorization of intervals into steps and skips is determined by the [[Musical tuning|tuning system]] and the [[pitch space]] used.

[[Melodic motion]] in which the interval between any two consecutive pitches is no more than a step, or, less strictly, where skips are rare, is called ''stepwise'' or ''conjunct'' melodic motion, as opposed to ''skipwise'' or ''disjunct'' melodic motions, characterized by frequent skips.

=== Enharmonic intervals ===
{{Main|Enharmonic}}
[[File:Enharmonic tritone.png|thumb|right|Enharmonic tritones: A4 = d5 on C[[File:Tritone on C.mid]]]]
Two intervals are considered ''[[enharmonic]]'', or ''enharmonically equivalent'', if they both contain the same [[Pitch (music)|pitches]] spelled in different ways; that is, if the notes in the two intervals are themselves enharmonically equivalent. Enharmonic intervals span the same number of [[semitone]]s.

For example, the four intervals listed in the table below are all enharmonically equivalent, because the notes F{{music|sharp}} and G{{music|b}} indicate the same pitch, and the same is true for A{{music|sharp}} and B{{music|b}}. All these intervals span four semitones.

{|class="wikitable"
! rowspan="2" ; style="text-align: left" | Number<br/>of semitones || rowspan="2" ; style="text-align: left" | Interval name || colspan="4"| [[Staff position]]s
|-
! 1 || 2 || 3 || 4
|-
| 4 || [[major third]] || F{{music|sharp}} || &nbsp; || A{{music|sharp}} || &nbsp;
|-
| 4 || major third || &nbsp; || G{{music|flat}} || &nbsp; || B{{music|flat}}
|-
| 4 || [[diminished fourth]] || F{{music|sharp}} || &nbsp; || &nbsp; || B{{music|flat}}
|-
| 4 || doubly [[augmented second]] || &nbsp; || G{{music|flat}} || A{{music|sharp}} || &nbsp;
|}

When played as isolated chords on a [[piano keyboard]], these intervals are indistinguishable to the ear, because they are all played with the same two keys. However, in a musical context, the [[diatonic function]] of the notes these intervals incorporate is very different.

The discussion above assumes the use of the prevalent tuning system, [[12-tone equal temperament]] ("12-TET"). But in other historic [[meantone temperament]]s, the pitches of pairs of notes such as F{{music|sharp}} and G{{music|b}} may not necessarily coincide. These two notes are enharmonic in 12-TET, but may not be so in another tuning system. In such cases, the intervals they form would also not be enharmonic. For example, in [[quarter-comma meantone]], all four intervals shown in the example above would be different.

== Minute intervals ==
[[File:Pythagorean comma on C.png|thumb|right|Pythagorean comma on C; the note depicted as lower on the staff (B[[semitone#Just intonation|{{music|#}}]][[syntonic comma|+++]]) is slightly higher in pitch (than C{{music|natural}}).[[File:Pythagorean comma on C.mid]]]]
{{Main | Comma (music) | Microtone}}
There are also a number of minute intervals not found in the chromatic scale or labeled with a diatonic function, which have names of their own. They may be described as [[microtone]]s, and some of them can be also classified as [[Comma (music)|comma]]s, as they describe small discrepancies, observed in some tuning systems, between [[enharmonic|enharmonically equivalent]] notes. In the following list, the interval sizes in [[cent (music)|cents]] are approximate.
* A ''[[Pythagorean comma]]'' is the difference between twelve justly tuned perfect fifths and seven octaves. It is expressed by the [[frequency]] ratio 531441:524288 (23.5 cents).
* A ''[[syntonic comma]]'' is the difference between four justly tuned perfect fifths and two octaves plus a major third. It is expressed by the ratio 81:80 (21.5 cents).
* A ''[[septimal comma]]'' is 64:63 (27.3 cents), and is the difference between the Pythagorean or 3-limit "7th" and the "harmonic 7th".
* A ''[[diesis]]'' is generally used to mean the difference between three justly tuned major thirds and one octave. It is expressed by the ratio 128:125 (41.1 cents). However, it has been used to mean other small intervals: see [[diesis]] for details.
* A ''[[diaschisma]]'' is the difference between three octaves and four justly tuned perfect fifths plus two justly tuned major thirds. It is expressed by the ratio 2048:2025 (19.6 cents).
* A ''[[schisma]]'' (also skhisma) is the difference between five octaves and eight justly tuned fifths plus one justly tuned major third. It is expressed by the ratio 32805:32768 (2.0 cents). It is also the difference between the Pythagorean and syntonic commas. (A schismic major third is a schisma different from a just major third, eight fifths down and five octaves up, F{{music|flat}} in C.)
* A ''[[kleisma]]'' is the difference between six [[minor third]]s and one ''tritave'' or ''perfect twelfth'' (an [[octave]] plus a [[perfect fifth]]), with a frequency ratio of 15625:15552 (8.1 cents) ({{Audio|Kleisma on C.mid|Play}}).
* A ''[[septimal kleisma]]'' is the amount that two major thirds of 5:4 and a septimal major third, or supermajor third, of 9:7 exceeds the octave. Ratio 225:224 (7.7 cents).
* A ''[[quarter tone]]'' is half the width of a [[semitone]], which is half the width of a [[major second|whole tone]]. It is equal to exactly 50 cents.

== Compound intervals ==
[[File:Simple and compound major third.png|thumb|Simple and compound major third[[File:Simple and compound major third.mid]]]]

A compound interval is an interval spanning more than one octave.<ref name="compound" /> Conversely, intervals spanning at most one octave are called simple intervals (see [[#Main intervals|Main intervals]] below).

In general, a compound interval may be defined by a sequence or "stack" of two or more simple intervals of any kind. For instance, a major tenth (two staff positions above one octave), also called ''compound major third'', spans one octave plus one major third.

Any compound interval can be always decomposed into one or more octaves plus one simple interval. For instance, a major seventeenth can be decomposed into two octaves and one major third, and this is the reason why it is called a compound major third, even when it is built by adding up four fifths.

The diatonic number ''DN''<sub>c</sub> of a compound interval formed from ''n'' simple intervals with diatonic numbers ''DN''<sub>1</sub>, ''DN''<sub>2</sub>, ..., ''DN''<sub>n</sub>, is determined by:
:<math>DN_c = 1 + (DN_1 - 1) + (DN_2 - 1) + ... + (DN_n - 1), \ </math>
which can also be written as:
:<math>DN_c = DN_1 + DN_2 + ... + DN_n - (n - 1), \ </math>

The quality of a compound interval is determined by the quality of the simple interval on which it is based. For instance, a compound major third is a major tenth (1+(8−1)+(3−1) = 10), or a major seventeenth (1+(8−1)+(8−1)+(3−1) = 17), and a compound perfect fifth is a perfect twelfth (1+(8−1)+(5−1) = 12) or a perfect nineteenth (1+(8−1)+(8−1)+(5−1) = 19). Notice that two octaves are a fifteenth, not a sixteenth (1+(8−1)+(8−1) = 15). Similarly, three octaves are a twenty-second (1+3×(8−1) = 22), four octaves are a twenty-ninth (1+3×(8-1) = 29), and so on.

=== Main compound intervals ===
{|class="wikitable"
|-
! Number of<br/>[[semitone]]s|| [[#Quality|Minor, major,<br/>or perfect]] intervals || Short || [[#Quality|Augmented or<br/>diminished]] intervals || Short
|-
| 12 || || || Diminished [[ninth]] || d9
|-
| 13 || [[Minor ninth]] || m9 || [[Augmented octave]] || A8
|-
| 14 || [[Major ninth]] || M9 || Diminished tenth || d10
|-
| 15 || [[Minor tenth]] || m10 || [[Augmented ninth]] || A9
|-
| 16 || [[Major tenth]] || M10 || Diminished [[eleventh]] || d11
|-
| 17 || [[Perfect eleventh]] || P11 || Augmented tenth || A10 
|-
| rowspan="2"| 18 || rowspan="2"| || rowspan="2"| || Diminished twelfth || d12
|-
| [[Augmented eleventh]] || A11
|-
| 19 || [[Perfect twelfth]] or [[Tritave]] || P12 || Diminished [[thirteenth]] || d13
|-
| 20 || Minor [[thirteenth]] || m13 || Augmented twelfth || A12
|-
| 21 || Major [[thirteenth]] || M13 || Diminished fourteenth || d14
|-
| 22 || Minor fourteenth || m14 || Augmented [[thirteenth]] || A13
|-
| 23 || Major fourteenth || M14 || Diminished [[fifteenth]] || d15
|-
| 24 || Perfect [[fifteenth]] or Double octave || P15 || Augmented fourteenth || A14
|-
| 25 || || || Augmented [[fifteenth]] || A15
|}

It is also worth mentioning here the major seventeenth (28 semitones)—an interval larger than two octaves that can be considered a multiple of a perfect fifth (7 semitones) as it can be decomposed into four perfect fifths (7 × 4 = 28 semitones), or two octaves plus a major third (12 + 12 + 4 = 28 semitones). Intervals larger than a major seventeenth seldom come up, most often being referred to by their compound names, for example "two octaves plus a fifth"<ref>Aikin, Jim (2004). ''A Player's Guide to Chords and Harmony: Music Theory for Real-World Musicians'', p.&nbsp;24. {{ISBN|0-87930-798-6}}.</ref> rather than "a 19th".

== Intervals in chords ==
{{Main|Chord (music)|Chord names and symbols (jazz and pop music)}}
Chords are sets of three or more notes. They are typically defined as the combination of intervals starting from a common note called the [[root (chord)|root]] of the chord. For instance a [[major triad]] is a chord containing three notes defined by the root and two intervals (major third and perfect fifth). Sometimes even a single interval ([[dyad (music)|dyad]]) is considered a chord.<ref name="Otto">[[Ottó Károlyi|Károlyi, Ottó]] (1965), ''Introducing Music'', p.&nbsp;63. Hammondsworth (England), and New York: Penguin Books. {{ISBN|0-14-020659-0}}.</ref> Chords are classified based on the quality and number of the intervals that define them.

=== Chord qualities and interval qualities ===
The main chord qualities are [[Major chord|major]], [[Minor chord|minor]], [[Augmented chord|augmented]], [[Diminished seventh chord|diminished]], [[half-diminished seventh chord|half-diminished]], and [[dominant chord|dominant]].
The [[Chord symbol|symbols]] used for chord quality are similar to those used for interval quality (see above). In addition, '''+''' or '''aug''' is used for augmented, '''°''' or '''dim''' for diminished, '''{{music|halfdim}}''' for half diminished, and '''dom''' for dominant (the symbol '''−''' alone is not used for diminished).

=== Deducing component intervals from chord names and symbols ===
The main rules to decode chord ''names or symbols'' are summarized below. Further details are given at [[Chord names and symbols (jazz and pop music)#Rules to decode chord names and symbols|Rules to decode chord names and symbols]].
# For 3-note chords ([[Triad (music)|triads]]), [[Major third|major]] or [[Minor third|minor]] always refer to the interval of the third above the [[root (chord)|root note]], while [[Augmented fifth|augmented]] and [[Diminished fifth|diminished]] always refer to the interval of the fifth above root. The same is true for the corresponding symbols (e.g., Cm means C<sup>m3</sup>, and C+ means C<sup>+5</sup>). Thus, the terms third and [[perfect fifth|fifth]] and the corresponding symbols 3 and 5 are typically omitted. This rule can be generalized to all kinds of chords,{{efn|name=rule1|General rule 1 achieves consistency in the interpretation of symbols such as CM<sup>7</sup>, Cm<sup>6</sup>, and C+<sup>7</sup>. Some musicians legitimately prefer to think that, in CM<sup>7</sup>, M refers to the seventh, rather than to the third. This alternative approach is legitimate, as both the third and seventh are major, yet it is inconsistent, as a similar interpretation is impossible for Cm<sup>6</sup> and C+<sup>7</sup> (in Cm<sup>6</sup>, m cannot possibly refer to the sixth, which is major by definition, and in C+<sup>7</sup>, + cannot refer to the seventh, which is minor). Both approaches reveal only one of the intervals (M3 or M7), and require other rules to complete the task. Whatever is the decoding method, the result is the same (e.g., CM<sup>7</sup> is always conventionally decoded as C–E–G–B, implying M3, P5, M7). The advantage of rule 1 is that it has no exceptions, which makes it the simplest possible approach to decode chord quality. {{pb}}
According to the two approaches, some may format the major seventh chord as CM<sup>7</sup> (general rule 1: M refers to M3), and others as C<sup>M7</sup> (alternative approach: M refers to M7). Fortunately, even C<sup>M7</sup> becomes compatible with rule 1 if it is considered an abbreviation of CM<sup>M7</sup>, in which the first M is omitted. The omitted M is the quality of the third, and is deduced according to rule 2 (see above), consistently with the interpretation of the plain symbol C, which by the same rule stands for CM.
}} provided the above-mentioned qualities appear immediately after the root note, or at the beginning of the chord name or symbol. For instance, in the chord symbols Cm and Cm<sup>7</sup>, m refers to the interval m3, and 3 is omitted. When these qualities do not appear immediately after the root note, or at the beginning of the name or symbol, they should be considered [[#Quality|interval qualities]], rather than chord qualities. For instance, in Cm<sup>M7</sup> ([[minor major seventh chord]]), m is the chord quality and refers to the m3 interval, while M refers to the M7 interval. When the [[#Number|number]] of an extra interval is specified immediately after chord quality, the quality of that interval may coincide with chord quality (e.g., CM<sup>7</sup> = CM<sup>M7</sup>). However, this is not always true (e.g., Cm<sup>6</sup> = Cm<sup>M6</sup>, C+<sup>7</sup> = C+<sup>m7</sup>, CM<sup>11</sup> = CM<sup>P11</sup>).{{efn|name=rule1}} See [[Chord names and symbols (jazz and pop music)#Rules to decode chord names and symbols|main article]] for further details.
# Without contrary information, a [[major third]] interval and a [[perfect fifth]] interval ([[major triad]]) are implied. For instance, a C chord is a C major triad, and the name C minor seventh (Cm<sup>7</sup>) implies a minor 3rd by rule 1, a perfect 5th by this rule, and a [[Minor seventh|minor 7th]] by definition (see below). This rule has one exception (see next rule).
# When the fifth interval is [[Diminished fifth|diminished]], the third must be minor.{{efn|name=rule4|All triads are [[Chord (music)#Secundal, tertian, and quartal chords|tertian]] chords (chords defined by sequences of thirds), and a major third would produce in this case a non-tertian chord. Namely, the diminished fifth spans 6 semitones from root, thus it may be decomposed into a sequence of two [[minor third]]s, each spanning 3 semitones (m3 + m3), compatible with the definition of tertian chord. If a major third were used (4 semitones), this would entail a sequence containing a major second (M3 + M2 {{=}} 4 + 2 semitones {{=}} 6 semitones), which would not meet the definition of tertian chord.}} This rule overrides rule 2. For instance, Cdim<sup>7</sup> implies a diminished 5th by rule 1, a minor 3rd by this rule, and a diminished 7th by definition (see below).
#Names and symbols that contain only a plain [[#Number|interval number]] (e.g., "seventh chord") or the [[root (chord)|chord root]] and a number (e.g., "C seventh", or C<sup>7</sup>) are interpreted as follows:
#*If the number is 2, 4, 6, etc., the chord is a major [[added tone chord]] (e.g., C<sup>6</sup> = C<sup>M6</sup> = C<sup>add6</sup>) and contains, together with the implied major triad, an extra [[Major second|major 2nd]], [[Perfect fourth|perfect 4th]], or [[Major sixth|major 6th]] (see [[Chord names and symbols (jazz and pop music)#Added tone chords|names and symbols for added tone chords]]).
#*If the number is 7, 9, 11, 13, etc., the chord is [[Dominant chord|dominant]] (e.g., C<sup>7</sup> = C<sup>dom7</sup>) and contains, together with the implied major triad, one or more of the following extra intervals: minor 7th, major 9th, perfect 11th, and major 13th (see names and symbols for [[Chord names and symbols (jazz and pop music)#Seventh chords|seventh]] and [[Chord names and symbols (jazz and pop music)#Extended chords|extended chords]]).
#*If the number is 5, the chord (technically not a chord in the traditional sense, but a [[dyad (music)|dyad]]) is a [[power chord]]. Only the root, a perfect fifth and usually an octave are played.

The table shows the intervals contained in some of the main chords ('''component intervals'''), and some of the symbols used to denote them. The interval qualities or numbers in '''[[boldface]]''' font can be deduced from chord name or symbol by applying rule 1. In symbol examples, C is used as chord root.

{|class="wikitable"
|-
!colspan="2"| Main [[Chord (music)|chords]]
!colspan="3"| Component intervals
|-
!Name
![[Chord symbol|Symbol]] examples
!Third
!Fifth
!Seventh
|-
| rowspan="2" | [[Major triad]] || C || M3 || P5 ||
|-
| CM, or Cmaj || '''M'''3 || P5 ||
|-
| [[Minor triad]] || Cm, or Cmin || '''m'''3 || P5 ||
|-
| [[Augmented triad]] || C+, or Caug || M3 || '''A'''5 ||
|-
| [[Diminished triad]] || C{{music|dimdeg}}, or Cdim || m3 || '''d'''5 ||
|-
| [[Dominant seventh chord]] || C<sup>7</sup>, or C<sup>dom7</sup> || M3 || P5 || m'''7'''
|-
| [[Minor seventh chord]] || Cm<sup>7</sup>, or Cmin<sup>7</sup> || '''m'''3 || P5 || m'''7'''
|-
| [[Major seventh chord]] || CM<sup>7</sup>, or Cmaj<sup>7</sup> || '''M'''3 || P5 || M'''7'''
|-
|[[Augmented seventh chord]]|| C+<sup>7</sup>, Caug<sup>7</sup>,<br/> C<sup>7{{Music|sharp}}5</sup>, or C<sup>7aug5</sup> || M3 || '''A'''5 || m'''7'''
|-
| [[Diminished seventh chord]] || C{{music|dimdeg}}<sup>7</sup>, or Cdim<sup>7</sup> || m3 || '''d'''5 || d'''7'''
|-
| [[Half-diminished seventh chord]] || C{{music|halfdim}}<sup>7</sup>, Cm<sup>7{{Music|flat}}5</sup>, or Cm<sup>7dim5</sup> || m3 || '''d'''5 || m'''7'''
|}

== Size of intervals used in different tuning systems ==
   <!-- Three articles link to this section:
        [[Pythagorean tuning]], [[1/4-comma meantone]], [[5-limit tuning]]
   -->

{| class="wikitable" style="text-align: center"
|- style="vertical-align:bottom;"
!rowspan=2| Number of<br/>semitones
!rowspan=2 style="text-align: left"| Name
!rowspan=2| [[5-limit tuning#Twelve tone scale|5-limit tuning]]<br/>(pitch ratio)
!colspan=4| Comparison of interval width (in cents)
|-
! [[5-limit tuning#Twelve tone scale|5-limit tuning]]
! [[Pythagorean tuning|Pythagorean<br/>tuning]]
! [[Quarter-comma meantone|{{1/4}}-comma<br/>meantone]]
! [[Equal temperament|Equal<br/>temperament]]
|-
| 0 ||align="left"| Perfect unison || '''1:1''' ||align="right"| '''0''' ||align="right"| '''0''' ||align="right"| '''0''' ||align="right"| '''0'''
|-
| 1 ||align="left"| Minor second || '''16:15'''<br/>27:25 ||align="right"| '''112'''<br/>133||align="right"| 90 ||align="right"| 117 ||align="right"| 100
|-
| 2 ||align="left"| Major second || '''9:8'''<br/>10:9 ||align="right"| '''204'''<br/>182 ||align="right"| '''204''' ||align="right"| 193 ||align="right"| 200
|-
| 3 ||align="left"| Minor third || '''6:5'''<br/>32:27||align="right"| '''316'''<br/>294 ||align="right"| 294<br/>318 ||align="right"| 310<br/>[[Wolf interval|(wolf)]] 269 ||align="right"| 300
|-
| 4 ||align="left"| Major third || '''5:4''' || align="right" | '''386''' ||align="right"| 408<br/>384 ||align="right"| '''386'''<br/>[[Wolf interval|(wolf)]] 427 ||align="right"| 400
|-
| 5 ||align="left"| Perfect fourth || '''4:3'''<br/>27:20 ||align="right"| '''498'''<br/>520 ||align="right"| '''498'''<br/>[[Wolf interval|(wolf)]] 522 ||align="right"| 503<br/>[[Wolf interval|(wolf)]] 462 ||align="right"| 500
|-
| 6 ||align="left"| Augmented fourth <br/> Diminished fifth || '''45:32'''<br/>'''25:18''' ||align="right"| '''590'''<br/>'''569''' ||align="right"| 612<br/>588 ||align="right"| 579<br/>621 ||align="right"| 600
|-
| 7 ||align="left"| Perfect fifth || '''3:2'''<br/>40:27 || align="right" | '''702'''<br/>680 ||align="right"| '''702''' <br/>[[Wolf interval|(wolf)]] 678 ||align="right"| 697<br/>[[Wolf interval|(wolf)]] 738 ||align="right"| 700
|-
| 8 ||align="left"| Minor sixth || '''8:5''' ||align="right"| '''814''' ||align="right"| 792 ||align="right"| '''814''' ||align="right"| 800
|-
| 9 ||align="left"| Major sixth || '''5:3'''<br/>27:16||align="right"| '''884'''<br/>906 ||align="right"| 906 ||align="right"| 890 ||align="right"| 900
|-
| 10 ||align="left"| Minor seventh || '''16:9'''<br/>9:5 ||align="right"| '''996'''<br/>1018 ||align="right"| '''996''' ||align="right"| 1007 ||align="right"| 1000
|-
| 11 ||align="left"| Major seventh || '''15:8'''<br/>50:27||align="right"| '''1088'''<br/>1067 ||align="right"| 1110 ||align="right"| 1083 ||align="right"| 1100
|-
| 12 ||align="left"| Perfect octave || '''2:1''' ||align="right"| '''1200''' ||align="right"| '''1200''' ||align="right"| '''1200''' ||align="right"| '''1200'''
|}

In this table, the interval widths used in four different tuning systems are compared. To facilitate comparison, [[just interval]]s as provided by 5-limit tuning (see [[5-limit tuning#Twelve tone scale|symmetric scale n.1]]) are shown in '''[[boldface|bold]]''' font, and the values in cents are [[Rounding|rounded]] to integers. Notice that in each of the [[just intonation|non-equal]] tuning systems, by definition the width of ''each'' type of interval (including the semitone) changes depending on the note that starts the interval. This is the art of [[just intonation]]. In [[equal temperament]], the intervals are never precisely in tune with each other. This is the price of using equidistant intervals in a 12-tone scale. For simplicity, for some types of interval the table shows only one value (the [[mode (statistics)|most often observed]] one).

In [[Quarter-comma meantone|{{1/4}}-comma meantone]], by definition 11 perfect fifths have a size of approximately 697 cents (700&nbsp;−&nbsp;''ε'' cents, where ''ε''&nbsp;≈&nbsp;3.42 cents); since the average size of the 12 fifths must equal exactly 700 cents (as in equal temperament), the other one must have a size of about 738 cents (700&nbsp;+&nbsp;11''ε'', the [[wolf fifth]] or [[diminished sixth]]); 8 major thirds have size about 386 cents (400&nbsp;−&nbsp;4''ε''), 4 have size about 427 cents (400&nbsp;+&nbsp;8''ε'', actually [[diminished fourth]]s), and their average size is 400 cents. In short, similar differences in width are observed for all interval types, except for unisons and octaves, and they are all multiples of ε (the difference between the {{1/4}}-comma meantone fifth and the average fifth). A more detailed analysis is provided at [[Quarter-comma meantone#Size of intervals|{{1/4}}-comma meantone Size of intervals]]. {{1/4}}-comma meantone was designed to produce just major thirds, but only 8 of them are just (5:4, about 386 cents).

The [[Pythagorean tuning]] is characterized by smaller differences because they are multiples of a smaller ''ε'' (''ε''&nbsp;≈&nbsp;1.96 cents, the difference between the Pythagorean fifth and the average fifth). Notice that here the fifth is wider than 700 cents, while in most [[meantone temperament]]s, including {{1/4}}-comma meantone, it is tempered to a size smaller than 700. A more detailed analysis is provided at {{slink|Pythagorean tuning|Size of intervals}}.

The [[5-limit tuning]] system uses just tones and semitones as building blocks, rather than a stack of perfect fifths, and this leads to even more varied intervals throughout the scale (each kind of interval has three or four different sizes). A more detailed analysis is provided at {{slink|5-limit tuning|Size of intervals}}. 5-limit tuning was designed to maximize the number of just intervals, but even in this system some intervals are not just (e.g., 3 fifths, 5 major thirds and 6 minor thirds are not just; also, 3 major and 3 minor thirds are [[wolf interval]]s).

The above-mentioned symmetric scale 1, defined in the 5-limit tuning system, is not the only method to obtain [[just intonation]]. It is possible to construct juster intervals or just intervals closer to the equal-tempered equivalents, but most of the ones listed above have been used historically in equivalent contexts. In particular, the [[5-limit tuning#Twelve tone scale|asymmetric version]] of the 5-limit tuning scale provides a juster value for the minor seventh (9:5, rather than 16:9). Moreover, the [[tritone]] (augmented fourth or diminished fifth), could have other just ratios; for instance, 7:5 (about 583 cents) or 17:12 (about 603 cents) are possible alternatives for the augmented fourth (the latter is fairly common, as it is closer to the equal-tempered value of 600 cents). The 7:4 interval (about 969 cents), also known as the [[harmonic seventh]], has been a contentious issue throughout the history of music theory; it is 31 cents flatter than an equal-tempered minor seventh. For further details about reference ratios, see {{slink|5-limit tuning|The justest ratios}}.

In the diatonic system, every interval has one or more ''[[enharmonic]] equivalents'', such as [[augmented second]] for [[minor third]].

== Interval root ==<!-- [[Interval root]] redirects here -->
[[Image:Harmonic series intervals.png|thumb|center|400px|Intervals in the [[harmonic series (music)|harmonic series]]]]
Although intervals are usually designated in relation to their lower note, [[David Cope]]<ref name="Cope"/> and [[Paul Hindemith|Hindemith]]<ref>[[Paul Hindemith|Hindemith, Paul]] (1934). ''The Craft of Musical Composition''. New York: Associated Music Publishers. Cited in Cope (1997), p.&nbsp;40–41.</ref> both suggest the concept of '''interval root'''. To determine an interval's root, one locates its nearest approximation in the harmonic series. The root of a perfect fourth, then, is its ''top'' note because it is an octave of the fundamental in the hypothetical harmonic series. The bottom note of every odd diatonically numbered intervals are the roots, as are the tops of all even numbered intervals. The root of a collection of intervals or a chord is thus determined by the interval root of its strongest interval.

As to its usefulness, Cope<ref name="Cope"/> provides the example of the final tonic chord of some popular music being traditionally analyzable as a "submediant six-five chord" ([[added sixth chord]]s by popular terminology), or a [[first inversion]] seventh chord (possibly the dominant of the mediant V/iii). According to the interval root of the strongest interval of the chord (in first inversion, CEGA), the perfect fifth (C–G), is the bottom C, the tonic.

== Interval cycles ==<!-- This section is linked from [[Symmetry]] -->
{{Main|Interval cycle| Identity (music)}}
[[Interval cycle]]s, "unfold [i.e., repeat] a single recurrent interval in a series that closes with a return to the initial pitch class", and are notated by [[George Perle]] using the letter "C", for cycle, with an interval-class integer to distinguish the interval. Thus the diminished-seventh chord would be C3 and the augmented triad would be C4. A superscript may be added to distinguish between transpositions, using 0–11 to indicate the lowest pitch class in the cycle.<ref name="Perle">[[George Perle|Perle, George]] (1990). ''The Listening Composer'', p.&nbsp;21. California: University of California Press. {{ISBN|0-520-06991-9}}.</ref>

== Alternative interval naming conventions ==
As shown below, some of the above-mentioned intervals have alternative names, and some of them take a specific alternative name in [[Pythagorean tuning]], [[five-limit tuning]], or meantone temperament tuning systems such as [[quarter-comma meantone]]. All the intervals with prefix ''sesqui-'' are [[just intonation|justly]] tuned, and their [[Interval ratio|frequency ratio]], shown in the table, is a [[superparticular number]] (or epimoric ratio). The same is true for the octave.

Typically, a [[Comma (music)|comma]] is a diminished second, but this is not always true (for more details, see [[Comma (music)#Alternative definitions|Alternative definitions of comma]]). For instance, in [[Pythagorean tuning]] the diminished second is a descending interval (524288:531441, or about −23.5 cents), and the [[Pythagorean comma]] is its opposite (531441:524288, or about 23.5 cents). 5-limit tuning defines [[Five-limit tuning#Commas|four kinds of comma]], three of which meet the definition of diminished second, and hence are listed in the table below. The fourth one, called [[syntonic comma]] (81:80) can neither be regarded as a diminished second, nor as its opposite. See [[Five-limit tuning#Diminished seconds|Diminished seconds in 5-limit tuning]] for further details.

{| class="wikitable"
|-
! rowspan="3"| Number of<br/>semitones!! colspan="4"|Generic names !! colspan="3"|Specific names
|-
! colspan="2"| [[#Quality|Quality]] and [[#Number|number]] !! colspan="2" rowspan="2"| Other naming convention !! rowspan="2"|[[Pythagorean tuning]] !! rowspan="2"|[[5-limit tuning]] !! rowspan="2"|[[Quarter-comma meantone|{{1/4}}-comma<br/>meantone]]
|-
! Full !! Short
|-
| rowspan="3"| 0 || [[perfect unison]]<br/> or perfect prime || P1 || colspan="2"| || || ||
|-
| rowspan="2"| [[diminished second]] || rowspan="2"| d2 || rowspan="2" colspan="2"| || rowspan="2"| descending<br/>[[Pythagorean comma]]<br/>(524288:531441) || colspan="2" style="text-align:center;"| lesser [[diesis]] (128:125)
|-
| [[diaschisma]] (2048:2025)<br/>greater diesis (648:625) ||
|-
| rowspan="2"| 1 || [[minor second]] || m2 || rowspan="2"| [[semitone]],<br/>half tone,<br/>half step || diatonic semitone,<br/>major semitone ||[[Pythagorean limma|limma]] (256:243) || ||
|-
| [[augmented unison]] <br/> or augmented prime|| A1 || chromatic semitone,<br/>minor semitone ||[[Pythagorean apotome|apotome]] (2187:2048) || ||
|-
| 2 || [[major second]] || M2 || colspan="2"| tone, [[whole tone]], whole step || colspan="2" style="text-align: center" | [[sesquioctavum]] (9:8) ||
|-
| 3 || [[minor third]] || m3 || colspan="2"| || || [[sesquiquintum]] (6:5) ||
|-
| 4 || [[major third]] || M3 || colspan="2"| || || colspan="2" style="text-align: center"| [[sesquiquartum]] (5:4)
|-
| 5 || [[perfect fourth]] || P4 || colspan="2"| || colspan="2" style="text-align: center" | [[sesquitertium]] (4:3) ||
|-
| rowspan="2"| 6 || [[diminished fifth]] || d5 || rowspan="2" colspan="2"| [[tritone]]{{efn|name=TritoneA4}} || || ||
|-
| [[augmented fourth]]|| A4 || || ||
|-
| 7 || [[perfect fifth]]|| P5 || colspan="2"| || colspan="2" style="text-align: center" | [[Superparticular ratio|sesquialterum]] (3:2) ||
|-
| 12 || [[octave|perfect octave]] || P8 || colspan="2"| || colspan="3" style="text-align: center" | duplex (2:1)
|}

Additionally, some cultures around the world have their own names for intervals found in their music. For instance, 22 kinds of intervals, called [[Shruti (music)|shrutis]], are canonically defined in [[Indian classical music]].

===Latin nomenclature===
Up to the end of the 18th century, [[Latin]] was used as an official language throughout Europe for scientific and music textbooks. In music, many English terms are derived from Latin. For instance, [[semitone]] is from Latin ''{{Lang|la|semitonus}}''.

The prefix semi- is typically used herein to mean "shorter", rather than "half".<ref>Gioseffo Zarlino, ''Le Istitutione harmoniche ... nelle quali, oltre le materie appartenenti alla musica, si trovano dichiarati molti luoghi di Poeti, d'Historici e di Filosofi, si come nel leggerle si potrà chiaramente vedere'' (Venice, 1558): 162.</ref><ref>{{ill|Jan Frederik Niermeyer|de|lt=J. F. Niermeyer}}, ''Mediae latinitatis lexicon minus: Lexique latin médiéval–français/anglais: A Medieval Latin–French/English Dictionary'', abbreviationes et index fontium composuit C. van de Kieft, adiuvante G. S. M. M. Lake-Schoonebeek (Leiden: E. J. Brill, 1976): 955. {{ISBN|90-04-04794-8}}.</ref><ref>''Robert De Handlo: The Rules, and Johannes Hanboys, The Summa: A New Critical Text and Translation'', edited and translated by Peter M. Lefferts. Greek & Latin Music Theory 7 (Lincoln: University of Nebraska Press, 1991): 193fn17. {{ISBN|0803279345}}.</ref> Namely, a semitonus, semiditonus, semidiatessaron, semidiapente, semihexachordum, semiheptachordum, or semidiapason, is shorter by one semitone than the corresponding whole interval. For instance, a semiditonus (3 semitones, or about 300 cents) is not half of a ditonus (4 semitones, or about 400 cents), but a ditonus shortened by one semitone. Moreover, in [[Pythagorean tuning]] (the most commonly used tuning system up to the 16th century), a semitritonus (d5) is smaller than a tritonus (A4) by one [[Pythagorean comma]] (about a quarter of a semitone).

{|class="wikitable"
|-
! Number of<br/>semitones|| [[#Quality|Quality]] and [[#Number|number]] || Short || Latin<br/>nomenclature
|-
| 0 || Perfect unison || P1 || {{lang|la|unisonus}}
|-
| rowspan="2"| 1 || Minor second || m2 || {{lang|la|semitonus}}
|-
| Augmented unison || A1 || {{lang|la|unisonus superflua}}
|-
| rowspan="2"| 2 || Major second || M2 || {{lang|la|tonus}}
|-
| [[Diminished third]] || d3 ||
|-
| rowspan="2"| 3 || Minor third || m3 || {{lang|la|semiditonus}}
|-
| [[Augmented second]] || A2 || {{lang|la|tonus superflua}}
|-
| rowspan="2"| 4 || Major third || M3 || {{lang|la|ditonus}}
|-
| [[Diminished fourth]] || d4 || {{lang|la|semidiatessaron}}
|-
| rowspan="2"| 5 || Perfect fourth || P4 || {{lang|la|diatessaron}}
|-
| [[Augmented third]] || A3 || {{lang|la|ditonus superflua}}
|-
| rowspan="2"| 6 || Diminished fifth || d5 || {{lang|la|semidiapente, semitritonus}}
|-
| Augmented fourth || A4 || {{lang|la|tritonus}}
|-
| rowspan="2"| 7 || Perfect fifth || P5 || {{lang|la|diapente}}
|-
| [[Diminished sixth]] || d6 || {{lang|la|semihexachordum}}
|-
| rowspan="2"| 8 || Minor sixth || m6 || {{lang|la|hexachordum minus, semitonus maius cum diapente, tetratonus}}
|-
| [[Augmented fifth]] || A5 || {{lang|la|diapente superflua}}
|-
| rowspan="2"| 9 || Major sixth || M6 || {{lang|la|hexachordum maius, tonus cum diapente}}
|-
| [[Diminished seventh]] || d7 || {{lang|la|semiheptachordum}}
|-
| rowspan="2"| 10 || Minor seventh || m7 || {{lang|la|heptachordum minus, semiditonus cum diapente, pentatonus}}
|-
| [[Augmented sixth]] || A6 || {{lang|la|hexachordum superflua}}
|-
| rowspan="2"| 11 || Major seventh || M7 || {{lang|la|heptachordum maius, ditonus cum diapente}}
|-
| [[Diminished octave]] || d8 || {{lang|la|semidiapason}}
|-
| rowspan="2"| 12 || Perfect octave || P8 || {{lang|la|diapason}}
|-
| [[Augmented seventh]] || A7 || {{lang|la|heptachordum superflua}}
|}

== Non-diatonic intervals ==
{{further|Neutral interval|Subminor and supermajor}}

Intervals in non-diatonic scales can be named using analogs of the diatonic interval names, by using a diatonic interval of similar size and distinguishing it by varying the quality, or by adding other modifiers. For example, the just interval 7/6 may be referred to as a ''subminor third'', since it is ~267 cents wide, which is narrower than a minor third (300 cents in 12-TET, ~316 cents for the just interval 6/5), or as the ''[[septimal minor third]]'', since it is a [[7-limit]] interval. These names refer just to the individual interval's size, and the interval number need not correspond to the number of scale degrees of a (heptatonic) scale. This naming is particularly common in [[just intonation]] and [[microtonal]] scales.<ref name="xen-extended">{{cite web|url=https://en.xen.wiki/w/Extended-diatonic_interval_names |title=Extended-diatonic interval names |work=Xenharmonic wiki}}</ref>

The most common of these extended qualities are a [[neutral interval|'''neutral''' interval]], in between a minor and major interval; and [[subminor and supermajor|'''subminor''' and '''supermajor''' intervals]], respectively narrower than a minor or wider than a major interval. The exact size of such intervals depends on the tuning system, but they often vary from the diatonic interval sizes by about a [[quarter tone]] (50 cents, half a chromatic step). For example, the [[neutral second]], the characteristic interval of [[Arabic music]], in 24-TET is 150 cents, exactly halfway between a minor second and major second. Combined, these yield the progression ''diminished, subminor, minor, neutral, major, supermajor, augmented'' for seconds, thirds, sixths, and sevenths. This naming convention can be extended to unisons, fourths, fifths, and octaves with ''sub'' and ''super'', yielding the progression ''diminished, sub, perfect, super, augmented''. This allows one to name all intervals in 24-TET or 31-TET, the latter of which was used by [[Adriaan Fokker]]. Various further extensions are used in [[Xenharmonic music]].<ref name="xen-extended"/>

== Pitch-class intervals ==
{{Main| Interval class| Ordered pitch interval}}

In post-tonal or [[atonality|atonal]] theory, originally developed for equal-tempered European classical music written using the [[twelve-tone technique]] or [[serialism]], [[integer notation]] is often used, most prominently in [[set theory (music)|musical set theory]]. In this system, intervals are named according to the number of half steps, from 0 to 11, the largest interval class being 6.

In atonal or musical set theory, there are numerous types of intervals, the first being the [[ordered pitch interval]], the distance between two pitches upward or downward. For instance, the interval from C upward to G is 7, and the interval from G downward to C is −7. One can also measure the distance between two pitches without taking into account direction with the unordered pitch interval, somewhat similar to the interval of tonal theory.

The interval between pitch classes may be measured with ordered and unordered pitch-class intervals. The ordered one, also called directed interval, may be considered the measure upwards, which, since we are dealing with pitch classes, depends on whichever pitch is chosen as 0. For unordered pitch-class intervals, see [[interval class]].<ref>{{Cite Grove |last=Roeder |first=John |title=Interval Class}}</ref>

== Generic and specific intervals ==
{{Main|Specific interval | Generic interval}}
In [[diatonic set theory]], [[specific interval|specific]] and [[generic interval]]s are distinguished. Specific intervals are the interval class or number of semitones between scale steps or collection members, and generic intervals are the number of diatonic scale steps (or staff positions) between notes of a collection or scale.

Notice that staff positions, when used to determine the conventional interval number (second, third, fourth, etc.), are counted including the position of the lower note of the interval, while generic interval numbers are counted excluding that position. Thus, generic interval numbers are smaller by 1, with respect to the conventional interval numbers.

=== Comparison ===
{| class="wikitable" style="text-align: center"
|- style="vertical-align:bottom;"
! colspan="2" | [[Specific interval]]
! rowspan="2" | [[Generic interval]]
! rowspan="2" style="text-align: left"| Diatonic name
|-
! Number of semitones
! [[Interval class]]
|-
| 0 || 0 || 0 ||align="left"| Perfect unison
|-
| 1 || 1 || 1 ||align="left"| Minor second
|-
| 2 || 2 || 1 ||align="left"| Major second
|-
| 3 || 3 || 2 ||align="left"| Minor third
|-
| 4 || 4 || 2 ||align="left"| Major third
|-
| 5 || 5 || 3 ||align="left"| Perfect fourth
|-
| 6 || 6 || 3 <br/> 4 ||align="left"| Augmented fourth <br/> Diminished fifth
|-
| 7 || 5 || 4 ||align="left"| Perfect fifth
|-
| 8 || 4 || 5 ||align="left"| Minor sixth
|-
| 9 || 3 || 5 ||align="left"| Major sixth
|-
| 10 || 2 || 6 ||align="left"| Minor seventh
|-
| 11 || 1 || 6 ||align="left"| Major seventh
|-
| 12 || 0 || 7 ||align="left"| Perfect octave
|}

== Generalizations and non-pitch uses ==
[[File:Time-point series.png|thumb|upright=1.2|Division of the measure/chromatic scale, followed by pitch/time-point series[[File:Time-point series.mid]]]]

The term "interval" can also be generalized to other music elements besides pitch. [[David Lewin]]'s ''Generalized Musical Intervals and Transformations'' uses interval as a generic measure of distance between [[time-point|time point]]s, [[timbre]]s, or more abstract musical phenomena.<ref>[[David Lewin|Lewin, David]] (1987). ''Generalized Musical Intervals and Transformations'', for example sections 3.3.1 and 5.4.2. New Haven: Yale University Press. Reprinted Oxford University Press, 2007. {{ISBN|978-0-19-531713-8}}</ref><ref>Ockelford, Adam (2005). ''Repetition in Music: Theoretical and Metatheoretical Perspectives'', p.&nbsp;7. {{ISBN|0-7546-3573-2}}. "Lewin posits the notion of musical 'spaces' made up of elements between which we can intuit 'intervals'....Lewin gives a number of examples of musical spaces, including the diatonic gamut of pitches arranged in scalar order; the 12 pitch classes under equal temperament; a succession of time-points pulsing at regular temporal distances one time unit apart; and a family of durations, each measuring a temporal span in time units....transformations of timbre are proposed that derive from changes in the spectrum of partials..."</ref>

For example, an interval between two bell-like sounds, which have no pitch salience, is still perceptible. When two tones have similar acoustic spectra (sets of partials), the interval is just the distance of the shift of a tone spectrum along the frequency axis, so linking to pitches as reference points is not necessary. The same principle naturally applies to pitched tones (with similar harmonic spectra), which means that intervals can be perceived "directly" without pitch recognition. This explains in particular the predominance of [[Interval recognition|interval hearing]] over [[absolute pitch]] hearing.<ref name="Tanguiane1993">{{Cite book|last=Tanguiane (Tangian) |first=Andranick|author-link=Andranik Tangian|date=1993|title= Artificial Perception and Music Recognition|series= Lecture Notes in Artificial Intelligence|volume=746|publisher=Springer |location=Berlin-Heidelberg|isbn=978-3-540-57394-4}}</ref><ref name="Tangian1994">{{Cite journal |last=Tanguiane (Tangian)|first=Andranick|author-link=Andranik Tangian|year=1994|title= A principle of correlativity of perception and its application to music recognition|journal=[[Music Perception]]|volume=11 |issue=4 |pages=465–502|doi= 10.2307/40285634 |jstor=40285634 }}</ref>

== See also ==
{{Portal|Music}}
* [[Circle of fifths]]
* [[Ear training]]
* [[List of meantone intervals]]
* [[List of pitch intervals]]
* [[Music and mathematics]]
* [[Pseudo-octave]]
* [[Regular temperament]]

== Notes ==
{{Notelist|45em}}

== References ==
{{Reflist|30em}}

===Sources===
* {{cite book|last=Helmholtz|first=H. L. F. von|author-link=Hermann von Helmholtz|orig-year=1877|title=On the Sensations of Tone as a Theoretical Basis for the Theory of Music|title-link=Sensations of Tone|edition=3rd English|translator=[[Alexander John Ellis]]|year=1895|publisher=[[Longmans, Green, and Co.]]}}

== External links ==
* Gardner, Carl E. (1912): [https://archive.org/details/essentialsofmusi00gard ''Essentials of Music Theory''], p.&nbsp;38
* [https://www.britannica.com/eb/article-9042627/interval "Interval"], ''[[Encyclopædia Britannica]]''
* [http://gerdbreitenbach.de/lissajous/lissajous.html Lissajous Curves: Interactive simulation of graphical representations of musical intervals, beats, interference, vibrating strings]
* [https://archive.org/details/1918elementsofhar00emeruoft Elements of Harmony: Vertical Intervals]
* {{YouTube|jNbCoU1lPFo|Just intervals, from the unison to the octave, played on a drone note}}

{{Intervals}}
{{Consonance and dissonance}}
{{Melody}}
{{Authority control}}

{{DEFAULTSORT:Interval}}
[[Category:Intervals (music)| ]]