Timbral effects on consonance illuminate psychoacoustics of music evolution

The phenomenon of musical consonance is an essential feature in diverse musical styles. The traditional belief, supported by centuries of Western music theory and psychological studies, is that consonance derives from simple ( harmonic) frequency ratios between tones. Here we show through massive large-scale behavioral experiments (235,440 judgments) that harmonic consonance preferences can be deeply reshaped by timbral manipulations, even as far as to induce preferences for inharmonic intervals. We show how such effects may have shaped the cultural evolution of diverse scale systems ranging from the gamelans slendro scale to the tuning of Western mean-tone and equal-tempered scales. Through computational modeling we show that these timbral manipulations elegantly dissociate competing psychoacoustic mechanisms underlying consonance, and we derive an updated computational model combining liking of harmonicity, disliking of fast beats (roughness), and liking of slow beats. Altogether, this work showcases how large-scale behavioral experiments can inform classical questions in auditory perception. Author summary"We reveal effects of timbre on consonance perception that motivate a new understanding of the evolution of musical scales."