Primary triad

Primary triads in C

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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.^[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 vii^o (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:

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

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

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

ii Dm
iii Em
vi Am

In A minor these are:^[3]

ii^o Bdim
III C
VI F

Sources

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

Chords

By form

Triad	Major Minor Augmented Diminished Suspended

Seventh	Major Minor Dominant Dominant seventh flat five Diminished Half-diminished Diminished major Minor-major Augmented major Augmented minor Altered seventh Nondominant Harmonic seventh

Extended	Ninth Eleventh Thirteenth Upper structure Dominant 7♯9 Polychord Tone cluster

Added / omitted	Sixth Augmented sixth Lydian Seven six

Specific	Alpha Bridge Complexe sonore Dream Elektra Farben Grandmother Magic µ Mystic Northern lights Petrushka Psalms So What Tristan Viennese trichord

General	Mixed interval Secundal Tertian Quartal Synthetic chord

By function

Diatonic	Tonic Dominant Subdominant Supertonic Mediant Submediant Leading / Subtonic

Altered	Approach Borrowed Chromatic mediant Neapolitan Passing

Secondary	Secondary dominant Secondary leading-tone Secondary supertonic

Other	Common Contrast Primary triad Subsidiary

Techniques

Other

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Primary triad

See also

Sources