View source for Tertian

{{Short description|Harmonic structures constructed from intervals of thirds}}
{{other uses|Tertials|Tertian fever|Tertianship}}
[[File:Tercera de picardía i iv i v I.png|thumb|400px|A progression of tertian chords in A minor (i-v-i-iv<math>{}^6_4</math>-i-v-I) ending on a [[Picardy third]] {{audio|Picardy third i iv i v I.mid|play}}]]
{{wiktionary}}

In [[music theory]], '''''tertian''''' ({{langx|la|tertianus}}, "of or concerning thirds") describes any [[piece (music)|piece]], [[chord (music)|chord]], [[counterpoint]] etc. constructed from the [[Interval (music)|intervals]] of ([[major third|major]] and [[minor third|minor]]) thirds.<ref>Benward & Saker (2009). ''Music in Theory and Practice'', Vol. II, p.370. {{ISBN|978-0-07-310188-0}}. "Tertian (third based) harmony".</ref> An interval such as that between the notes A and C encompasses 3 [[semitone]] intervals (A-B{{music|b}}-B{{music|natural}}-C) and is termed a [[Minor mode|minor]] third while one such as that between C and E encompasses 4 semitones (C-D{{music|b}}-D{{music|natural}}-E{{music|b}}-E{{music|natural}}) and is called a [[Major mode|major]] third. '''Tertian harmony''' (also called '''tertiary harmony'''<ref>{{Cite Grove |author= |title=Tertiary harmony}} {{full citation needed|date=July 2020}}</ref>) principally uses chords based on thirds; the term is typically used to contrast with [[quartal and quintal harmony]] which uses chords based on fourths or fifths.

[[Image:Quartal chord on A equals thirteenth chord on Bb.png|thumb|right|Quartal chord on A equals [[thirteenth|thirteenth chord]] on B{{music|b}}, distinguished by the [[Voicing (music)|arrangement]] of [[factor (chord)|chord factors]] {{audio|Quartal chord on A equals thirteenth chord on Bb.mid|Play}}.<ref>Benward & Saker (2009), p.279.</ref>]]

A common [[Triad (music)|triad]] chord can be regarded as consisting of a "stack" of two consecutive thirds. This allows for four permutations, each producing a chord with distinct [[Chord quality|quality]]:
{| class="wikitable"
|+
! colspan="2" |Quality of Third
! rowspan="2" |Resulting
Chord Quality
|-
!1st 
!2nd
|-
|major
|minor
|major
|-
|minor
|major
|minor
|-
|major
|major
|augmented
|-
|minor
|minor
|diminished
|}

A musical scale may also be analyzed as a [[Ladder of thirds|succession of thirds]].

The [[meantone temperament]], a system of tuning that emphasizes pure thirds, may be called "tertian".

Chords built from [[Sixth interval|sixths]] may also be referred to as tertian because sixths are equivalent to thirds when [[Inversion (interval)|inverted]], and vice versa: any sixth can be taken as the inversion of a third. For instance, the interval C-A is a major sixth that, when inverted, gives the interval A-C, which is a minor third.

Tertian root movements have been used innovatively in [[chord progression]]s as an alternative to root motion in fifths, as for example in the "thirds cycle" used in John Coltrane's [[Coltrane changes]], as influenced by [[Nicolas Slonimsky]]'s ''Thesaurus of Scales and Melodic Patterns''.

==See also==
* [[Major and minor]]
* [[Mediant]] and [[submediant]]
* [[Secundal]]
* [[Quartal and quintal harmony|Quartal]]
* [[Polychord]]

==References==
<references/>

{{Chords}}

[[Category:Chords]]
[[Category:Thirds (music)]]