Bebop scale

Bebop scale is a term referring to the practice of adding a note (typically a chromatic passing tone) to any common seven tone scale in order to make it an eight tone scale. Having eight notes enables the primary chord tones to continuously fall on the on-beats when the scale is played sequentially. This is unlike common seven note scales in which the chord tones do not all naturally fall on the on-beats due to an odd number of notes. These bebop scales are frequently used in jazz improvisation.^[1] Jazz educator David Baker nicknamed these scales the "bebop scales" because they were used often by jazz artists from the Bebop Era. These artists include Charlie Christian, Charlie Parker, Bud Powell, and Dizzy Gillespie, to name a few.

In general, bebop scales consist of traditional scales with an added passing tone, and when the scale is played from any chord tone and placed on any on-beat, then all other chord tones will also continuously fall on on-beats. Chord tones on on-beats are characteristic of all strong melodies throughout musical history. The remaining notes in the scale are non-chord tones and all fall on the off-beats.

As such, generally, any scale of seven notes may be modified by the addition of an additional note to accomplish the same effect allowing chord tones to naturally stay on the beat. The modifier "bebop" is reserved to indicate those modified scales most frequently used—and popularized—during the bebop era.