Quantitative, randomised controlled trials (RCTs) or quasi-experimental studies of adults that included music interventions (with or without other non-pharmacological methods) in patients who had undergone surgery were eligible for inclusion. Eligible studies were required to use postoperative pain as an outcome measure. Studies that used sounds instead of music were excluded.
The included studies were performed in the USA, Sweden, Japan, Hong Kong, China and Taiwan. Participants ranged from 15 to 86 years old (where stated) and were scheduled for different surgical procedures that varied in complexity. The interventions used in addition to music included therapeutic suggestions, guided imagery, scheduled rest, jaw relaxation and decreased noise levels. Most of the control groups received usual care or listened to a blank tape or compact disc. In most of the studies participants could choose music from tapes or compact discs made by the investigators; in other studies the research team selected the music, participants brought their own music, or (in one study) a live harpist played their own selection of music. The timing of the the intervention and the time at which assessments were made varied between studies. The instruments used to assess pain were: the visual analogue scale (VAS), the numeric rating scale (NRS), the verbal rating scale (VRS), the Wong-Baker Faces Scale, and the graphic numeric pain intensity scale. Analgesic consumption was also measured in some studies.
One reviewer performed selected studies for inclusion.