Chimeric music reveals an interaction of pitch and time in electrophysiological signatures of music encoding

Abstract

Pitch and time are the essential dimensions defining musical melody. Recent electrophysiological studies have explored the neural encoding of musical pitch and time by leveraging probabilistic models of their sequences, but few have studied how the features might interact. This study examines these interactions by introducing "chimeric music," which pairs two distinct melodies, and exchanges their pitch contours and note onset-times to create two new melodies, thereby distorting musical pattern while maintaining the marginal statistics of the original pieces pitch and temporal sequences. Through this manipulation, we aimed to dissect the music processing and the interaction between pitch and time. Employing the temporal response function (TRF) framework, we analyzed the neural encoding of melodic expectation and musical downbeats in participants with varying levels of musical training. Our findings revealed differences in the encoding of melodic expectation between original and chimeric stimuli in both dimensions, with a significant impact of musical experience. This suggests that the structural violation due to decoupling the pitch and temporal structure affect expectation processing. In our analysis of downbeat encoding, we found an enhanced neural response when participants heard a note that aligned with the downbeat during music listening. In chimeric music, responses to downbeats were larger when the note was also a downbeat in the original music that provided the pitch sequence, indicating an effect of pitch structure on beat perception. This study advances our understanding of the neural underpinnings of music, emphasizing the significance of pitch-time interaction in the neural encoding of music. Significance StatementListening to music is a complex and multidimensional auditory experience. Recent studies have investigated the neural encoding of pitch and timing sequences in musical structure, but they have been studied independently. This study addresses the gap in understanding of how the interaction between pitch and time affects their encoding. By introducing "chimeric music," which decouples these dimensions in melodies, we investigate how this interaction influences the neural activities using EEG. Leveraging and the temporal response function (TRF) framework, we found that structural violations in pitch-time interactions impact musical expectation processing and beat perception. These results advance our knowledge of how the brain processes complex auditory stimuli like music, underscoring the critical role of pitch and time interactions in music perception.