The diatonic chord of major key are Imaj7, IIm7, IIIm7, IVmaj7, V7, VIm7, VIIm7(b5)
The main functions are:
- Tonic : Imaj7, IIIm7, VIm7
- Sub dominant : IVmaj7, IIm7 (VIm7)
- Dominant : V7, VIIm7(b5) (IIIm7)
The diatonic chords can be classified to these functions showed above.
Stability in a tonal.
Instability in a tonal, and it is followed by both tonic(unstable → stability) and dominant(unstable → more instability).
IV → I
- 3 → 5
- R → 3
- 3 → R
V7 decides a tonal by resolving a tritone.
- 3rd → Root
- 7th → 3rd
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.