A new eBook is available for download. It contains 50 exercises with guitar tabs and standard music notation that will show you how to use different types of voicings over a II-V-I progression. This PDF eBook will help you to understand how the main jazz guitar chords are built (minor 7, major 7, dominant 7, diminished 7, half-diminished, augmented, 7b5, drop 2, drop 3, inverted, altered, extended and rootless chords) and how to apply chord substitutions (diatonic sub, tritone sub and diminished substitutions).
One of the most popular jazz chord substitution is the tritone substitution sometimes referred to as the dominant chord substitution.
It consists in replacing the V with a dominant 7th chord whose root is a tritone below. Example with G7 (V), which can be replaced by Db7 a tritone (Three whole-steps) away.
Thus giving two chords that have two notes in common. The 7th of G7 (F) is the third of Db7 and the third of G7 (B) is the seventh of Db7. The inversion of the 3rds and the 7ths between the original dominant chord (V) and the substituted dominant chord (bII7) is the main feature of the tritone substitution.