Tritone Substitutions

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Replacing a dominant seventh chord with the dominant seventh chord a tritone (diminished fifth or augmented fourth) away is a simple way to enrich an otherwise diatonic progression. Consider the following ii-V-I progression:

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Replacing the V chord with the dominant seventh chord a tritone away yields a ii-bII-I progression:

[EXAMPLE]

This is illustrated at top. When you see a dominant seventh chord, as in the first measure, you can replace it with the dominant seventh chord a tritone away, as in the second measure at top.

There are several reasons this substitution works well. For one thing, in a ii-V-I progression that becomes a ii-bII-I, note that the new root resolves to the chord that follows by half step, which is a very strong motion melodically:

[EXAMPLE]

More importantly, recall that the third and seventh of a chord are the important notes with respect to function. In a tritone substitution, the third of one chord is enharmonic with the seventh of the other, and vice versa:

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Therefore, the chords sound alike in a fundamental way. Also, the root and fifth of one chord are the flat fifth and flat ninth respectively of the other:

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A scale that works with an unaltered dominant seventh chord will also work with an altered dominant seventh chord a tritone away. In fact, the lydian dominant scale built on one root is the same as the altered scale built on the other:

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Furthermore, the two HW diminished scales are identical, as are the respective whole tone scales:

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If you see an unaltered dominant seventh chord and you want to add color, and easy way to do it is to substitute the unaltered dominant seventh chord a tritone away. This creates the same effect as altering the original chord:

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Also, if you see an altered dominant seventh chord, an easy way to play over it is to substitute the unaltered dominant seventh a tritone away:

[EXAMPLE]

Copyright 2000 Outside Shore Music
Authored by Marc Sabatella

Tritone Substitutions