The cognitive framework for musical scales in various cultures

Musical scales in different cultures throughout the world share certain design features. This suggests that some general constraints influence scale structure. Some features of scales reflect constraints apparently grounded in the physical stimulus and perhaps the auditory system; for example, octave equivalence. Other features appear to derive from limitations on human information processing abilities; for example, the use of a limited number of discrete pitch levels. The latter seems to arise from the advantages of discrete categorization of elements in noisy communication channels, and cognitive limitations on the number of categories humans can handle at a time. Combining these two types of constraints further specifies the form that scales can take; octave equivalence combined with a limited number of pitch categories leads to scales having up to seven or so pitches per octave, with the pitch categories recycled through several octaves in a logarithmic pattern. Subtler constraints are discussed, and the resulting design features are illustrated with examples from several cultures.