Diatonic Chord

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Function

The diatonic chord of major key are Imaj7, IIm7, IIIm7, IVmaj7, V7, VIm7, VIIm7(b5)

The main functions are:

  1. Tonic : Imaj7, IIIm7, VIm7
  2. Sub dominant : IVmaj7, IIm7 (VIm7)
  3. Dominant : V7, VIIm7(b5) (IIIm7)

The diatonic chords can be classified to these functions showed above.

Tonic

Stability in a tonal.

Sub dominant

Instability in a tonal, and it is followed by both tonic(unstable → stability) and dominant(unstable → more instability).

Voice leading

IV → I

Voice Lading V-I

IV → I

  • 3 → 5
  • R → 3
Voice Lading IV-V

IV → V

  • 3 → R

Dominant

V7 decides a tonal by resolving a tritone.

Voice leading

Voice Lading V-I

V → I

  • 3rd → Root
  • 7th → 3rd

Sub Function

The main chord of each functions are: tonic is I, sub dominant is IV, dominant is V, and the other chords works as following effects in each functions.

  • Substitute : replace an original chord.
  • Extend : follow an original chord.
  • Delay : push an original chord back.