Convergent evolution in a large cross-cultural database of musical scales

Abstract

Scales, sets of discrete pitches used to generate melodies, are thought to be one of the most universal features of music. Despite this, we know relatively little about how cross-cultural diversity, or how scales have evolved. We remedy this, in part, we assemble a cross-cultural database of empirical scale data, collected over the past century by various ethnomusicologists. We provide statistical analyses to highlight that certain intervals (e.g., the octave) 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; for 7-note scales this accounts for less than 1% of all possible scales. In addition to providing these data and statistical analyses, we review how they may be used to explore the causes for convergent evolution in scales.

Timbral effects on consonance illuminate psychoacoustics of music evolution

“…2:1, 3:2). This would explain why scale systems across the world seem to have developed to favor harmonic pitch intervals (Gill & Purves, 2009; McBride & Tlusty, 2021). Within a given society, cultural familiarity will further contribute to consonance perception, biasing listeners towards preferring sonorities that occur often within a given musical style.…”

Musical scales optimize pitch spacing: A global analysis of traditional vocal music

“…Consecutive semitones were extremely rare in the vocal scales. When semitones occurred in scales, they tended to be padded by a larger interval on the other side, as seen in the major, minor, and Hijaz scales in instrumental music (see also 18 ). This overall picture is consistent with the predictions of the Interval Spacing model that scales seem to optimize pitch spacing in order to make adjacent pitch-classes distinguishable from one another in both production and perception.…”

“…Scales tend to contain 5-7 pitch-classes per octave, arranged in small step-like intervals of at least 1 semitone 12,13 , and more commonly 2-4 semitones 10,14 . Scales are often non-equidistant, meaning that they are comprised of at least two distinct interval-sizes 14,15 , although there is also evidence for equidistant scales in some cultures [16][17][18] . Most scales contain one tone as a reference for the others, known as the tonic pitch 14,19 .…”

“…Most scales contain one tone as a reference for the others, known as the tonic pitch 14,19 . They then typically contain pitch-classes that are approximately 2, 5, and 7 semitones above the tonic 18,[20][21][22][23][24] . They also tend to contain a pitch-class that is either roughly 3 or 4 semitones above the tonic (i.e., a minor third or major third, respectively) 25 , but only rarely both, and sometimes a neutral third 16 .…”