Tritone Substitution
Two dominant 7 chords, a tritone apart, sharing the exact same tension — swap one for the other and the resolution still works.
What is a tritone substitution?
Any dominant 7 chord can be replaced by another dominant 7 chord whose root sits a tritone (six semitones) away. In C major, the V7 chord is G7 (G–B–D–F). A tritone from G is Db, so the tritone substitution is Db7 (Db–F–Ab–Cb). Both chords resolve convincingly to C — jazz musicians notate the substitute chord subV7.
Why it works: the shared tritone
A dominant 7 chord's pull toward resolution comes from the tritone between its 3rd and 7th. G7's 3rd and 7th are B and F. Db7's 3rd and 7th are F and Cb — which is the same pitch as B, just respelled. Both chords contain the identical tritone; tritone substitution simply relabels which note is the 3rd and which is the 7th, and swaps the root a tritone away. The tension driving the resolution never actually goes away.
A smoother bass line for ii–V–I
In a jazz ii–V–I (Dm7–G7–Cmaj7), swapping in the tritone sub gives Dm7–Db7–Cmaj7 — the bass now walks down chromatically, D to Db to C, instead of leaping a 5th from G to C. That stepwise descending bass line is a huge part of why tritone substitution is such a signature sound in jazz reharmonization.
Common questions
What is a tritone substitution?
Replacing a dominant 7 chord with another dominant 7 chord a tritone away — they share the same tritone between their 3rd and 7th, so both resolve convincingly to the same tonic.
Why does tritone substitution work?
Both chords contain the identical 3rd/7th tritone, just with roles swapped, so the tension driving the resolution doesn't disappear when the root changes.
What is subV7?
Jazz notation for a tritone substitution. In a ii-V-I, replacing V7 with subV7 also creates a smooth chromatic descending bass line into the tonic.
Where is tritone substitution used?
It's a staple of jazz reharmonization, especially over ii-V-I progressions, adding chromatic color and stepwise bass motion.
Reharmonize any progression
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