22.60Your substitution toolbox

At this stage, know these categories:

Functional relatives

I ↔ vi / iii IV ↔ ii V ↔ vii°

Tritone substitute

V7 ↔ dominant 7 a tritone away

Example: G7 ↔ D♭7

Backdoor dominant

♭VII7 → I

Example: B♭7 → C

Common-tone substitute

Choose another chord preserving important melody/inner notes.

Diminished dominant substitute

vii°7 → I

Borrowed-function alternative

iv → I instead of V → I