Huge strikes in roots can correspond to small strikes in chords.
Think about the 12 notes of a chromatic scale organized across the hours of a clock: C at 12:00, C♯ at 1:00, D at 2:00, and so forth. The furthest aside two notes could be is 6 half steps, simply because the furthest aside two occasions could be is 6 hours.
An interval of 6 half steps is known as a tritone. That’s a standard time period in jazz. In classical music you’d doubtless say augmented fourth or diminished fifth. Similar factor.
The biggest attainable motion in roots corresponds to nearly the smallest attainable motion between chords. Particularly, to go from a dominant seventh chord to a different dominant seventh chord whose roots are a tritone aside solely requires transferring two notes of the chord a half step every.
For instance, C and F♯ are a tritone aside, however a C7 chord and a F♯7 chord are very shut collectively. To maneuver from the previous to the latter you solely want to maneuver two notes a half step.
Changing a dominant seventh chord with one a tritone away is known as a tritone substitution, or simply tritone sub. It’s referred to as this for 2 causes. The basis strikes a tritone, but additionally the tritone inside the chord does not transfer. Within the instance above, the third and the seventh of the C7 chord change into the seventh and third of the F♯7 chord. On the diagram, the dots at 4:00 and 10:00 don’t transfer.
Tritone substitutions are a standard method for making primary chord progressions extra refined. A standard tritone sub is to exchange the V of a ii-V-I chord development, giving a pleasant chromatic development within the bass line. For instance, in the important thing of C, a D min – G7– C development turns into D min – D♭7 – C.
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