26.50Level 17 — tritone substitution

G7 → Cm

becomes:

D♭7 → Cm

Now explore extensions.

D♭7:

D♭ F A♭ C♭.

The important guide tones:

F and B(C♭).

Then Cm:

E♭ and C.

Possible moves:

F → E♭

B → C.

Excellent.