tritone substitution
theoryTRY-tone sub
A jazz harmonic technique in which a dominant seventh chord is replaced by another dominant seventh chord a tritone away
Tritone substitution works because two dominant seventh chords a tritone apart share the same tritone interval (the third and seventh swap roles). In the key of C, G7 (containing B and F) can be replaced by D♭7 (also containing F and C♭/B). The substitution creates chromatic bass motion (D♭ to C instead of G to C), which many jazz musicians prefer for its smooth voice leading. Tritone subs are fundamental to bebop harmony and modern jazz arranging.