The Tritone Substitution

In C major

Dm7 – Db7 – Cmaj7 — slinky, chromatic, sophisticated, around 126 BPM.

1. Bar 1 iim7 Dm7
   D · F · A · C
   ▶ Hear it
2. Bar 2 bII7 Db7
   Db · F · Ab · B
   ▶ Hear it
3. Bar 3 Imaj7 Cmaj7
   C · E · G · B
   ▶ Hear it

Why it works

A dominant seventh's identity lives in its tritone — the interval between its third and seventh. Two dominant chords a tritone apart share that exact pair of notes, with the roles swapped, so either can resolve to the same tonic. Substituting turns a bass leap of a fourth into a chromatic step down a semitone, which is why the substitution is audible in the bass long before it is audible in the harmony.

Where you'll hear it

Turnarounds and any dominant that has already been heard once. Because the substitute is a semitone above the target, it also sets up chromatic approach chords elsewhere in the arrangement.

iim7–♭II7–Imaj7 in every key

The same progression transposed. The roman numerals never change — that is the whole point of writing progressions this way.

Related progressions

• iim7–V7–Imaj7 The ii–V–I Progression
• ivm7–♭VII7–Imaj7 The Backdoor ii–V
• Imaj7–vim7–iim7–V7 The Turnaround