Twirling Triplets: The Qualia of Rotation and Musical Rhythm

Triplet rhythms and other fast, repeated patterns with stepwise pitch movement are associated with sensations of rotation in listeners. An analysis of crowd-sourced musical excerpts found that compound meters are more common in such music than in Western music generally. An Ecological Theory of Rotating Sounds (ETRoS) proposes that loudness fluctuations in music mimic the acoustic patterns of rotating sound sources. Two experiments showed that perceived rotation increases with tempo and is weak for binary rhythms. Patterns with loudness stress matching rotating trajectories were rated as more rotating than typical Western patterns, but only when pitch also moved. The results offer moderate support for an acoustic-ecological explanation.

Study at a glance

Abstract

While musicologists have long noted that triplet rhythms evoke sensations of rotation in listeners, no theory has been proposed to account for this apparent association. To investigate this phenomenon, 33 excerpts of “spinning, rotating, twirling, or swirling” music were crowd-sourced from an online discussion forum. Analysis revealed a prominence of fast, repeated, isochronous patterns using stepwise pitch movement, with significantly more compound meters than generally found in Western music. Inspired by ecological acoustics, an Ecological Theory of Rotating Sounds (ETRoS) is proposed to explain these associations. The theory maps patterns of loudness fluctuations to trajectories of rotating sound sources. Two experiments tested the theory. In Experiment A, listeners rated how much binary, ternary, quaternary, and quinary figures (of 2–5 notes) evoked sensations of rotation. Experiment B used a two-alternative forced-choice paradigm pitting ecological quaternary stimuli (strong-medium-weak-medium) against unecological stimuli with permuted stress values more typical of Western music (strong-weak-medium-weak). Results indicate that perceived rotation increases with tempo and is poorly evoked by binary rhythms. Loudness patterns consistent with rotating trajectories were perceived as more rotating than unecological patterns—but only when pitch was also moving. Altogether, moderate support is provided for an acoustic-ecological account of rotating sounds.