Primary triad

Primary triads in C  Play .

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.[1] 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."[1] 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.

Diatonic functions in hierarchical order in C

In C major these are:

In a minor key triads i and iv are minor chords, but in chord V the leading note is generally raised to form a major chord.[2] For example, in A minor the primary triads are Am, Dm and E. Chord v (minor) in a minor key may be considered a primary triad, but its use is rare in common practice harmony.

Subdominant and subdominant parallel in C major: FM (IV) and Dm (ii) chords  Play .

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.[3] In C major these are:[3]

In A minor these are:[3]

See also


  1. 1 2 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
  2. Eric Taylor (2009). Music Theory in Practice Grade 4, p.22. ISBN 978-1-86096-945-4. ABRSM
  3. 1 2 3 Lancaster & Renfrow (2008). Alfred's Group Piano for Adults: Student Book 2, p.77. ISBN 0-7390-4925-9.
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