In jazz, a constant structure is a chord progression consisting of three or more chords of the same type or quality. [1] Popularized by pianists Bill Evans and Herbie Hancock, the combination of functional and nonfunctional chords provides cohesiveness while producing a free and shifting tonal center. [1] [2]
For example, the progression Fmaj7–A♭maj7–D♭maj7–G♭maj7–C13sus4 [1] contains four major seventh chords (and one thirteenth chord), none of which are diatonic to the key of F major except the first.
In contrast, the vi–ii–V–I or circle progression from classical theory contains four chords of two or three different qualities: major, minor, and possibly a dominant seventh chord; all of which, however, are diatonic to the key. Thus diversity is achieved within a stable and fixed tonal center.
