Jazz harmony
Tritone substitution, explained by ear
Any dominant seventh can be replaced by the dominant seventh a tritone away. G7 becomes D♭7, the bass slides down a semitone instead of falling a fifth, and the chord still lands where it was going.
Why it works
What makes G7 want to resolve is the tritone between its third, B, and its seventh, F. D♭7 has the same two notes: its third is F and its seventh is C♭, which sounds as B. Same tritone, swapped, so the same pull to C.
- Dm7ii7
- G7V7
- Cmaj7Imaj7
- Dm7ii7
- Cmaj7Imaj7
- 1 voice holds, 3 move, 6 semitones of motion in all.
- 0 voices hold, 4 move, 6 semitones of motion in all.
What changes is the bass
With the substitute, the roots move D, D♭, C: a chromatic line down to the tonic. That smooth bass is most of the sound. The upper voices barely move at all, which is why it is so easy to hear and so easy to overuse.
Substituting secondary dominants too
The same move works on any dominant, including secondary ones. E7 heading for Am can become B♭7, sliding down a semitone to A. Each major key page lists the substitute for every dominant in the key.
Every chord on this page is spelled and voiced by Tonalia's music engine.