21.45Tritone substitution preview

Here is an important jazz reharmonization device we'll study more fully in Module 22.

G7:

G B D F

The critical tritone:

B-F

Another dominant chord contains the same tritone enharmonically:

D♭7

D♭ F A♭ C♭(=B)

Guide tones:

F and C♭/B.

So:

D♭7 → C

can replace:

G7 → C

This is a tritone substitution.