Cortical and behavioural tracking of rhythm in music: Effects of pitch predictability, enjoyment, and expertise

The cortical tracking of stimulus features (such as the sound envelope) is a crucial neural requisite of how we process continuous music. We here tested whether cortical tracking of the beat, typically related to rhythm processing, is modulated by pitch predictability and other top-down factors. Participants listened to tonal (high pitch predictability) and atonal (low pitch predictability) music while undergoing EEG, and we analysed their cortical tracking of the acoustic envelope. Interestingly, cortical envelope tracking was stronger while listening to atonal than tonal music, likely reflecting listeners violated pitch expectations. Envelope tracking was also stronger with more expertise and enjoyment. Furthermore, we analysed cortical tracking of pitch surprisal (using IDyOM) and show that listeners expectations for tonal and atonal music match those computed by the IDyOM model, with higher surprisal (prediction errors) for atonal than tonal music. Behaviourally, we measured participants ability to tap along to the beat of tonal and atonal sequences in two experiments. In both experiments, finger-tapping performance was better in the tonal than the atonal condition, indicating a positive effect of pitch predictability on behavioural rhythm processing. Cortical envelope tracking predicted tapping performance for tonal music, as did pitch surprisal tracking for atonal music, indicating that conditions of high and low predictability might impose different processing regimes. We show that cortical envelope tracking, beyond reflecting musical rhythm processing, is modulated by pitch predictability, as well as musical expertise and enjoyment. Taken together, our results show various ways in which those top-down factors impact musical rhythm processing.