Diatonic scale are major scales (those with a major third/triad: Ionian, Lydian, and Mixolydian), three are minor (those with a minor third/triad: Dorian, Phrygian, and Aeolian). To these may be added the seventh diatonic scale, with a diminished fifth above the reference note, the Locrian scale. These could be transposed not only to include one flat in the signature (as described by Glarean), but to all twelve notes of the chromatic scale, resulting in a total of eighty-four diatonic scales. The modern musical keyboard originated as a diatonic keyboard with only white keys. The black keys were progressively added for several purposes:
Jazz scale scales add a single chromatic passing tone to the 7 note major scale (Ionian and Mixolydian modes). The added passing tone creates an 8 tone scale that fits rhythmically evenly within a 4/4 measure of eight 8th notes, thus making it useful in practicing. When an 8th note bebop scale run starts on the beat from a chord tone (Root, 3rd, 5th or 7th) the other chord notes will also fall on the beats. As a result, all of the "non-chord tones" will fall on the upbeats (the "ands" when counting "one and two and three and four and") and