Jazz Theory 19 - Appendix
DOUBLE TRITONE
Chord Substitutions

Back to Quiz 19 Answers



The diminished 7th chord is a symmetric chord.
This chord can be described as a stack of three minor 3rd intervals, or as two interlocking tritones.

Audio 1
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In Jazz the dim7 chord is commonly used to voice a dominant 7b9 chord with its root a major 3rd below any one of the chord's four notes.

This creates four different dominant chords all from the same diminished chord. The four dominant chords form two sets of tritone substitutes.

The 7b9 relationship of these four chords is not as strong as the tritone bond, but it is sufficient to form a basis for chord substitution in modern Jazz (even without the b9 in the dominant chord).

This generates the following possibilities for chord substitution :

Scale for Improvisation
C7 = Eb7 = Gb7 = A7 (C 8-note dominant scale)
G7 = Bb7 = Db7 = E7 (G 8-note dominant scale)
D7 = F7 = Ab7 = B7 (D 8-note dominant scale)

Each of the related IIm7 chords can also be placed in front of the substitute V7.
This produces :

Gm7 C7 = Bbm7 Eb7 = Dbm7 Gb7 = Em7 A7
Dm7 G7 = Fm7 Bb7 = Abm7 Db7 = Bm7 E7
Am7 D7 = Cm7 F7 = Ebm7 Ab7 = F#m7 B7

(You can even interchange the IIm7 chords within each substitute group.)

In bar 4 of Georgia the Bbm7 Eb7 chords are substitutes for Gm7 C7.
They represent a IIm7 V7 segment leading to Fmaj7.

Audio 2
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Musical judgment is essential when selecting a substitution for a particular musical setting.

When playing the melody make sure that a chord substitution does not clash with the melody notes.

With improvisations you have more freedom with substitutions, but include appropriate scales in your scale progression for improvisation. You can also use certain substitutions in one chorus, and others (or none) in the next.


I wish to acknowledge my former Jazz teacher Bruce Hancock (Head of the Jazz Department at Adelaide University) who explained the principle of double tritone substitution to me many years ago. I have not seen this principle explained properly in any Jazz Theory literature anywhere in the world.

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© 1998 - 2008 Michael Furstner (Jazclass)