Melody, not harmony, shapes global musical scales per 1,314-scale study

Researchers at multiple institutions, led by John M. McBride, used evolutionary modeling to analyze the structure of 1,314 musical scales drawn from 96 countries. They tested two competing theories: that scales are primarily shaped by harmonic principles (e.g., perfect fourths, fifths, octaves) versus melodic constraints (preferred step sizes of 1-3 semitones). The Melody model significantly outperformed the Harmony model in predicting real-world scale data, explaining the cross-cultural prevalence of intervals like whole steps and half steps. Harmony only contributed a weak additional bias toward fourths, fifths, and octaves—and that bias was concentrated in music-theoretic scales rather than scales measured directly from performances.

The findings challenge a tradition dating back to ancient Greece that treats harmony as the foundation of musical structure. The authors note that harmony's outsized influence in music theory likely stems from a historical focus on mathematically idealized scales from a few traditions (e.g., Western equal temperament) rather than empirical data from global musical practices. The study also validates its Melody model against independent data from melodies, singing, and psychoacoustics, showing near-universal preference for small interval steps. This has implications for music education, AI music generation, and our understanding of the evolutionary origins of music—suggesting melody, not harmony, may be the deeper cognitive universal.