Individual differences in the effects of musical familiarity and musical features on brain activity during relaxation.

Finding a way to relax is increasingly difficult in our overstimulating, modern society. Chronic stress can have severe psychological and physiological consequences. Music is a promising tool to promote relaxation by lowering heart rate, modulating mood and thoughts, and providing a sense of safety. We used functional magnetic resonance imaging to investigate how music influences brain activity during relaxation with a particular focus on the participants' experience of different types of music. In a 2 × 2 design, 57 participants were scanned while rating how relaxed they felt after listening to 28-s excerpts of either familiar or unfamiliar relaxation music with calm or energetic features. Behaviourally, calm music was the strongest predictor of relaxation, followed by familiar music. Functional magnetic resonance imaging results revealed activations of auditory, motor, emotion, and memory areas for listening to familiar compared with unfamiliar music. This suggests increased audiomotor synchronization and participant engagement of known music. Listening to unfamiliar music was correlated with attention-related brain activity, suggesting increased attentional load for this music. Behaviourally, we identified four clusters of participants based on their relaxation response to the different types of music. These groups also displayed distinct auditory and motor activity patterns, suggesting that the behavioural responses are linked to changes in music processing. Interestingly, some individuals found energetic music to be relaxing if it is familiar, whereas others only found calm music to be relaxing. Such individual behavioural and neurological differences in relaxation responses to music emphasise the importance of developing personalised music-based interventions.