Chord substitution

Tritone substitution: F♯7 may substitute for C7, and vice versa, because they both share E♮ and B♭/A♯ and due to voice leading considerations.
C7 is transpositionally equivalent to F♯7, the leading tones resolve inversionally (E–B♭ resolves to F–A, A♯–E resolves to B–D♯)
F–C7–F, F–F♯7–F, B–F♯7–B, then B–C7–B

In music theory, chord substitution is the technique of using a chord in place of another in a progression of chords, or a chord progression. Much of the European classical repertoire and the vast majority of blues, jazz and rock music songs are based on chord progressions. "A chord substitution occurs when a chord is replaced by another that is made to function like the original. Usually substituted chords possess two pitches in common with the triad that they are replacing."[1]

A chord progression may be repeated to form a song or tune. Composers, songwriters and arrangers have developed a number of ways to add variety to a repeated chord progression. There are many ways to add variety to music, including changing the dynamics (loudness and softness).

  1. ^ Blatter, Alfred (2007). Revisiting Music Theory: A Guide to the Practice, p. 186. ISBN 0-415-97440-2.