The structure of musical scales has been proposed to reflect universal bioacoustic principles based on simple integer ratios. However, some researchers who have studied tuning in small samples of non-Western cultures have argued that such ratios are instead specific to Western music. To address this debate, we algorithmically analyzed and cross-culturally compared scale tunings within a global sample of 124 music recordings, including both instrumental and vocal music. Although we found great cross-cultural diversity in most scale degrees, we also found a strong cross-cultural tendency to include the simplest possible integer ratios within the octave (3:2 ratio [perfect 5th] and 4:3 ratio [perfect 4th]). This suggests that cultural diversity in musical scales is not without limit, but is constrained by general bioacoustic principles, such as harmonic consonance in group performance, that may shed light on the evolution of human music.

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