Comparison 1. Sleep quality: listening to music versus control – Pittsburgh Sleep Quality Index (PSQI) – global score.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Sleep quality: Pittsburgh Sleep Quality Index (PSQI) – immediately postintervention	10	708	Mean Difference (IV, Random, 95% CI)	‐2.79 [‐3.86, ‐1.72]
1.2 Subgroup (PSQI) by duration of intervention – immediately postintervention	10	708	Mean Difference (IV, Random, 95% CI)	‐2.79 [‐3.86, ‐1.72]
1.2.1 Medium duration (8–21 days)	5	343	Mean Difference (IV, Random, 95% CI)	‐2.24 [‐2.90, ‐1.58]
1.2.2 Long duration (22–90 days)	5	365	Mean Difference (IV, Random, 95% CI)	‐3.36 [‐5.63, ‐1.10]
1.3 Subgroup (PSQI) by aetiology – immediately postintervention	9	644	Mean Difference (IV, Random, 95% CI)	‐2.82 [‐4.09, ‐1.56]
1.3.1 Age‐related sleep problems	3	184	Mean Difference (IV, Random, 95% CI)	‐2.78 [‐3.97, ‐1.58]
1.3.2 Insomnia related to medical conditions	3	276	Mean Difference (IV, Random, 95% CI)	‐3.87 [‐7.66, ‐0.08]
1.3.3 Insomnia disorder	2	63	Mean Difference (IV, Random, 95% CI)	‐2.47 [‐4.18, ‐0.76]
1.3.4 Pregnancy‐related insomnia	1	121	Mean Difference (IV, Random, 95% CI)	‐1.18 [‐2.35, ‐0.01]
1.4 Subgroup (PSQI) by music selection – immediately postintervention	10	708	Mean Difference (IV, Random, 95% CI)	‐2.79 [‐3.86, ‐1.72]
1.4.1 Researcher‐selected	5	370	Mean Difference (IV, Random, 95% CI)	‐3.31 [‐5.32, ‐1.29]
1.4.2 Participant‐selected (choice among researcher‐selected playlists)	5	338	Mean Difference (IV, Random, 95% CI)	‐2.33 [‐3.37, ‐1.29]
1.5 Subgroup (PSQI) by relaxation instructions – immediately postintervention	10	708	Mean Difference (IV, Random, 95% CI)	‐2.79 [‐3.86, ‐1.72]
1.5.1 Music listening alone	8	583	Mean Difference (IV, Random, 95% CI)	‐2.85 [‐4.18, ‐1.51]
1.5.2 Music listening and relaxation instructions	2	125	Mean Difference (IV, Random, 95% CI)	‐2.64 [‐3.74, ‐1.54]