Silverman 2019a.

Study characteristics
Methods	Study design: cluster RCT Study grouping: parallel group Allocation concealment: method for allocation concealment not specified Randomisation method: through 24 sessions, participants were cluster‐randomised into 3 groups via a computer program. Participants were allocated the group of the first session they attended.
Participants	Baseline characteristics MT (lyric analysis) + SC Gender male: 22 (50%) Age: 35.40 years Sample size: 44 MT (song writing) + SC Gender male: 20 (65%) Age: 37.10 years Sample size: 31 Recreational music + SC Gender male: 23 (61%) Age: 35.08 years Sample size: 38 Overall Gender male: 65 (58%) Age: 35.86 years Sample size: 113 Inclusion criteria: inpatient on short‐term detoxification unit (thus, with diagnosis of SUD); ability to read English Exclusion criteria: none mentioned Pretreatment: no significant differences between groups in regard to: number of people taking part in each session who volunteered to be research participants; total number of participants in each session; age; number of times they had been in rehabilitation/detoxification facility; gender; ethnic background; primary drug.
Interventions	Intervention characteristics MT (lyric analysis) + SC Description: MT scripted educational lyric analysis group session focused on relapse prevention, led by music therapist. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session MT (song writing) + SC Description: MT group songwriting session using blues genre and focusing on recovery, led by music therapist. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session Recreational music + SC Description: rock and roll music bingo led by music therapist, with some discussion of songs, artists, and associated memories. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session
Outcomes	Not used:  Group experience (Ferrara Group Experiences Scale)
Identification	Sponsorship source: none Country: USA Setting: inpatient detoxification unit of a large teaching hospital Author's name: Michael J Silverman Institution: University of Minnesota Email: silvermj@umn.edu Address: Music Therapy Department, University of Minnesota, Minneapolis, USA Declarations of interest: no conflicts of interest reported.
Notes	Email (25 March 2021) from author confirmed report is the same as the Silverman 2021.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Judgement comment: participants in 24 sessions were cluster randomised via a computer program into conditions by session.
Allocation concealment (selection bias)	Unclear risk	Judgement comment: insufficient information about allocation concealment to permit judgement.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: no incomplete outcome data.
Selective reporting (reporting bias)	Low risk	Judgement comment: no selective reporting.
Blinding of participants and providers (performance bias) (subjective outcomes)	Low risk	Judgement comment: not possible to blind participants and providers to MT intervention.
Blinding of outcome assessor (detection bias) (subjective outcomes)	Unclear risk	Judgement comment: not possible to blind outcome assessor for self‐report outcomes, though measurement not likely to be influenced differentially between groups.