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Primary triad
Type of musical chord / From Wikipedia, the free encyclopedia
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.
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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.
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In C major these are:
- I C
- V G
- IV F
- vi Am
- iii Em
- ii Dm
- viio 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 might be expected to be a primary triad, but its use is rare in common practice harmony.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Subdominant_parallel_in_C_major.png/640px-Subdominant_parallel_in_C_major.png)
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]
- iio Bdim
- III C
- VI F