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
Acoustic scale major sixth (D and A). Lendvai described the use of the "acoustic system" accompanying the acoustic scale in Bartók's music, since it entails structural characteristics such as symmetrically balanced sections, especially periods, is contrasted with his use of the golden section. In Bartók's music, the acoustic scale is characterized in various ways including diatonic, dynamic, tense, and triple- or other odd-metered, as opposed to the music structured by the Fibonacci sequence which is chromatic, static, relaxed, and duple-metered. Another way to regard the acoustic scale is that it occurs as a mode of the melodic minor scale, starting on the