If you took a quick survey and asked a few people to describe the components of bebop, you might come up with some answers like: “fast tempos, lots of notes, Charlie Parker, Dizzy Gillespie, b9’s, b5’s, altered dominants, diminished scales.”
While all of these are true of the music, one of the most overlooked, but surprisingly simple devices of bebop is that of super-imposing chords over existing changes.
Aside from the essential rhythmic and melodic characteristics of the music, the practice of reharmonizing common chord changes, whether implied melodically by the soloist or explicitly stated harmonically by the rhythm section, was crucial to the innovations of bebop.
Dizzy Gillespie talks about this concept in his book with Al Fraser, To Be, or Not…To Bop:
We found out what the composers were doing by analyzing these tunes, and then added substitute chords to songs like “Night and Day,” “How High the Moon,” “Lover,” “What is this Thing Called Love,” and “Whispering.” When we borrowed from a standard, we added and substituted so many chords that most people didn’t know what song we really were playing. “How High the Moon” became “Ornithology” and “What is this Thing Called Love” became “Hot House.” … That was our thing in bebop, putting in substitutions. (p.207)
Many of the reharmonization techniques of the musicians of the 1940’s centered around super-imposing or substituting progressions, most commonly through the use of ii-V7’s, over the existing progressions of traditional standards. These traditional pop-tunes were predominantly composed of basic harmonies: Major chords (triads), minor chords, & V7 chords, and contained simple chord progressions that had little harmonic motion.
The progression below is an example of a static V7 chord commonly found in these traditional tunes: