The tritone substitution II–V–I progression is a common jazz harmonic device that adds color and smooth voice leading to a traditional II–V–I chord change. To understand it, let’s first break down the basics.

A standard II–V–I progression in a key consists of three chords: the II chord (usually a minor seventh chord), the V chord (a dominant seventh chord), and the I chord (often a major seventh chord). For example, in the key of C major, the II chord is Dmin7, the V chord is G7, and the I chord is Cmaj7.

Tritone substitution replaces the dominant V chord with another dominant chord whose root lies a tritone (three whole steps) away. In jazz, this is often done to create smoother bass movement or introduce chromaticism. In the key of C, instead of playing G7 as the V chord, you replace it with Db7, because Db is a tritone away from G.

Why does this work? Both G7 and Db7 share two important notes in their chord tones—called the tritone interval—that create tension needing resolution. That tension resolves nicely to the I chord (Cmaj7), giving the progression a fresh twist.

So, a tritone substitution II–V–I progression in C major would be:

• II chord: Dmin7
• Substituted V chord: Db7 (instead of G7)
• I chord: Cmaj7

This substitution provides a smooth chromatic bass line moving from D down to Db and then to C, which can be more interesting both harmonically and melodically. It’s widely used in jazz improvisation and comping to add richness and unexpected colors to familiar progressions.