Tritone Substitution in Jazz Music

Tritone substitution is a very commonly used reharmonization technique in jazz music. It was first used by musicians such as Duke Ellington, Art Tatum, Coleman Hawkins, Roy Eldridge and Benny Goodman.

From Wikipedia:

A tritone substitution is the use in a chord progression of a dominant seventh chord (major/minor seventh chord) that is three whole steps (a tritone) away from the original dominant seventh chord. For example, Db7 would be the tritone substitution for G7.

In jazz voicing, the 3rd note and the 7th note shows the character of a chord. So it is very common when a pianist is playing comping, he can omit the root and the fifth, and voices the chord mostly with 3rd and 7th. The reason these dominant seventh chords may be substituted for each other is that they share the two pitches that form a tritone in each chord (the third and seventh, albeit reversed). In a G7 chord, the third is B and the seventh is F. In the Db7 chord, the third is an F and the seventh is Cb (enharmonically B). Note that the interval between the third and seventh of a dominant seventh chord is itself a tritone. Hence, we got the name “tritone” which is 3 tones equal to three whole steps or 6 semitones apart.

Why is tritone substitution solely for jazz music?

Now, you try to play the chord progression Dm7 - G7 - Cmaj7. Then alternatively replace the G7 with Db7, thus Dm7 - Db7 - C. You will hear a really jazzy harmony. This substitution is particularly suitable for jazz because it produces chromatic root movement when applied to the ii-V-I progression prevalent in jazz tunes. Substituting Db7 for G7 produces the downward movement D - Db - C in the roots of the chords, typically played by the bass. This also reinforces the downward movement of the thirds and sevenths of the chords in the progression (in this case, F/C to F/B to E/B).

Tritone subtitutions are also known as substitute dominants, or Sub-V (Sub-five) chords.

To see tritone substitution in action with video, transcription and analysis, check out these great posts:I Love You Porgy Advance Reharmonization Techniques

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Joe Pass Reharmonization on Autumn Leaves

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