Heptatonic scale are considered subsets of a twelve-pitch scale roughly analogous to the Western chromatic scale. The first and fifth melakarta tones, corresponding to the first and eighth chromatic tones, are invariable in inflection, and the fourth melakarta tone, corresponding to the sixth or seventh chromatic tone, is allowed one of two inflections only, a natural ("shuddah") position and a raised ("tivra") position. The second and third melakarta tones can be picked from the 4 chromatic tones (second through fifth), and similarly for the sixth and seventh. Thus the number of possible forms is equal to twice the square of the number
Yo scale A - B. This is illustrated below. The Ryūkyū scale appears to be derived from the yo scale with pitches raised. More recent theory emphasizes that it is more useful in interpreting Japanese melody to view scales on the basis of "nuclear tones" located a fourth apart and containing notes between them, as in the "min'yō" scale used in folk music, and whose pitches are equivalent to the second mode of the "yo" scale: Yo scale The "yo" scale, which does not contain minor notes, according to a traditional theory is a pentatonic scale used in much Japanese music including