  Scales, sets of discrete pitches that form the basis of melodies, are thought
to be one of the most universal hallmarks of music. But we know relatively
little about cross-cultural diversity of scales or how they evolved. To remedy
this, we assemble a cross-cultural database (Database of Musical Scales:
DaMuSc) of scale data, collected over the past century by various
ethnomusicologists. Statistical analyses of the data highlight that certain
intervals (e.g., the octave, fifth, second) are used frequently across
cultures. Despite some diversity among scales, it is the similarities across
societies which are most striking - most scales are found close to equidistant
5- and 7-note scales. We discuss the mechanisms of variation and selection in
the evolution of scales, and how the assembled data may be used to examine the
root causes of convergent evolution.
