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:
Double harmonic scale harmonic minor scales respectively, each of which, unlike the double harmonic minor scale, has a full diminished chord backbone. This scale (and its modes like the Hungarian minor scale) is the only seven-note scale (in 12-tone equal temperament) that is "perfectly balanced"; this means that when its pitches are represented as points on a circle (whose full circumference represents an octave), their average position (or "centre of mass") is the centre of the circle. Like most heptatonic (seven-pitch) scales, the double harmonic scale has a mode for each of its individual scale degrees. The most commonly known of these modes