The bebop scales are frequently used in jazz improvisation and are derived from the modes of the major scale, the melodic minor scale, and the harmonic minor scale.
David Baker, one of the world’s finest jazz educators, named these scales the “bebop scales” because they were used so often by jazz artists from the Bebop Era. These artists include Charlie Christian, Charlie Parker, Lester Young, and Dizzy Gillespie, to name a few.
There are four types of frequently used bebop scales: the bebop dominant scale, the bebop Dorian scale, the bebop major scale, and the bebop melodic minor scale. Each of these scales has an extrachromatic passing tone. In general, bebop scales consist of traditional scales with an added passing tone placed such that when the scale is begun on a chord tone and on the downbeat, all other chord tones will also fall on downbeats, with the remaining tones in the scale occurring on the upbeat (given that the scale is played ascending or descending; i.e., no intervallic skips are played). As such, many heptatonic scales may be modified by the addition of an eighth passing tone to accomplish this same effect; however, the modifier “bebop” is reserved to indicate those scales most frequently used—and popularized—during the bebop era (and/or by modern practitioners of the bebop genre).
David Baker, bebop scales, Vol.I
David Baker, Vol 2 – Learning the Bebop Language
David Baker Vol 3 – Techniques for Learning and Utilizing Bebop Tunes
Armonia – David Baker – Arranging and Composing
:>)azZTechs# 