Primary triad

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Type of musical chord

title: "Primary triad" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["chords"] description: "Type of musical chord" topic_path: "general/chords" source: "https://en.wikipedia.org/wiki/Primary_triad" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Type of musical chord ::

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In music, a primary triad is one of the three triads, or three-note chords built from major or minor thirds, most important in tonal and diatonic music, as opposed to an auxiliary triad or secondary triad.

Each triad found in a diatonic key corresponds to a particular diatonic function. Functional harmony tends to rely heavily on the primary triads: triads built on the tonic, subdominant, and dominant degrees. The roots of these triads begin on the first, fourth, and fifth degrees (respectively) of the diatonic scale, otherwise symbolized: I, IV, and V (again, respectively). Primary triads, "express function clearly and unambiguously." The other triads of the diatonic key include the supertonic, mediant, sub-mediant, and leading-tone, whose roots begin on the second, third, sixth, and seventh degrees (respectively) of the diatonic scale, otherwise symbolized: ii, iii, vi, and viio (again, respectively). They function as auxiliary or supportive triads to the primary triads.

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In C major these are:

I C
V G
IV F
vi Am
iii Em
ii Dm
vii Bdim

In a minor key triads i and iv are minor chords, but in chord V the leading-tone is generally raised to form a major chord. For example, in A minor the primary triads are Am, Dm and E. Chord v (minor) in a minor key might be expected to be a primary triad, but its use is rare in common practice harmony.

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Auxiliary chords may be considered parallel and contrast chords derived from the primary triads. For example, the supertonic, ii, is the subdominant parallel, relative of IV (in C: a d minor chord is the subdominant parallel, the subdominant is an F major chord). Being a parallel chord in a major key it is derived through raising the fifth a major second (C of F–A–C rises to D → F–A–D, an inversion of D–F–A). Alternatively, secondary triads may be considered ii, iii, and vi. In C major these are:

ii Dm
iii Em
vi Am

In A minor these are:

ii Bdim
III C
VI F

References

Harrison, Daniel (1994). ''Harmonic Function in Chromatic Music: A Renewed Dualist Theory and an Account of its Precedents'', p.45. {{ISBN. 0-226-31808-7. Cited in Deborah Rifkin. "A Theory of Motives for Prokofiev's Music", p.274, ''Music Theory Spectrum'', Vol. 26, No. 2 (Autumn, 2004), pp. 265-289. University of California Press on behalf of the Society for Music Theory
Eric Taylor (2009). ''Music Theory in Practice Grade 4'', p.22. {{ISBN. 978-1-86096-945-4. ABRSM
Lancaster & Renfrow (2008). ''Alfred's Group Piano for Adults: Student Book 2'', p.77. {{ISBN. 0-7390-4925-9.

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