Pleasantness of nonlinear distortion in isolated triads of synthetic timbre

Distortion of sound is an important tool to increase the variety of timbres in musical compositions, but perceived pleasantness of distortion is understudied, and studies are limited to guitar practices in rock and metal music. This study applied a more systematic approach, using synthetic timbre and creating an audio-plugin that realized nonlinear symmetric and asymmetric distortion. Participants evaluated the perceived pleasantness of isolated triads differing in distortion (undistorted, symmetric, asymmetric), tonality (minor, major), and position (low, high, wide), taking baseline differences of tonality and position into account. Perceived pleasantness decreased by distortion, and the decrease was stronger for minor than major triads and stronger for asymmetric than symmetric distortion. Position played only a minor role in the evaluations, except for stimuli in high positions. Stimulus-based analyses showed a relation between pleasantness and the variability of roughness, mean spectral centroid, and mean sound intensity. Subject-based analyses revealed a smaller decrease in pleasantness with a preference for electronic music. Importantly, some distorted triads were rated as pleasant in absolute terms: major triads with symmetric distortion in low or wide position. That is, indeed, distortion is not always categorized as unpleasant but can be perceived as pleasant.