Various "sixth" chords can be used in place of subdominant (the IV chord).
- Italian sixth
- V7 in IIb (without 5)
- French sixth
- V7 in IIb (with b5)
- connected to the blues pendulum
- German sixth
- V7 in IIb (with normal 5)
- Neapolitan sixth
- IIb triad
- V in the mirror key
- can be used over a minor or major chord
- major: IIb/I or V/Vb or IV/VIb or I/IIb
- minor: VIIb/I or IV/IV