"A team of UK researchers from Brunel University and Queen Mary University of London analyzed data from 72 trials involving nearly 7000 patients. They found that patients were significantly less anxious after surgery, and reported significantly more satisfaction, after listening to music.
Patients also needed less pain medication and reported significantly less pain compared with those who had not listened to music. Surprisingly, even listening to music while under general anaesthetic reduced patients’ levels of pain, although the effects were larger when patients were conscious.
Although listening to music at any time seemed effective, there was a trend for better outcomes if patients listened to music before surgery rather than during or after." Listening To Music Improves Recovery After Surgery - Sciencebeta.