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:
Symmetric scale degrees are symmetrical if read from the "top" (end) or "bottom" (beginning) of the scale (mirror symmetry). Examples include the Ukrainian Dorian b9 scale (sixth mode of the Hungarian Major scale), the Jazz Minor b5 scale (fifth mode of the involution of Hungarian Major), the Neapolitan Major scale (fourth mode of the Major Locrian scale), the Javanese slendro, the chromatic scale, whole-tone scale, Dorian scale, the Aeolian Dominant scale (fifth mode of the melodic minor), and the double harmonic scale. Asymmetric scales are "far more common" than symmetric scales and this may be accounted for by the inability of symmetric