Tritone substitution

The tritone substitution is a common chord substitution found in both jazz and classical music. Where jazz is concerned, it was the precursor to more complex substitution patterns like Coltrane changes. Tritone substitutions are sometimes used in improvisation—often to create tension during a solo. Though examples of the tritone substitution, known in the classical world as an augmented sixth chord, can be found extensively in classical music since the Renaissance period,^[1] they were not heard outside of classical music until they were brought into jazz by musicians such as Dizzy Gillespie and Charlie Parker in the 1940s,^[2] as well as Duke Ellington, Art Tatum, Coleman Hawkins, Roy Eldridge and Benny Goodman.^[3]

The tritone substitution can be performed by exchanging a dominant seventh chord for another dominant seventh chord which is a tritone away from it. For example, in the key of C major one can use D♭⁷ instead of G⁷ (D♭ is a tritone away from G, and G is the dominant of C).