Silverman 2015a.

Study characteristics
Methods	Study design: cluster RCT Study grouping: parallel group Allocation concealment: not specified Randomisation method: participants in 15 sessions were cluster randomised into conditions by session. The numbers 1–15 were randomised into 3 groups and each group was assigned to a condition. Not otherwise specified.
Participants	Baseline characteristics MT + SC Gender male: 13 (56.5%) Age: 42.43 years Sample size: 23 Verbal therapy + SC Gender male: 12 (57.1%) Age: 37.62 years Sample size: 21 Recreational music + SC Gender male: 15 (60%) Age: 36.04 years Sample size: 25 Overall Gender male: 40 (57.9%) Age: 38.69 years Sample size: 69 Inclusion criteria: inpatient on detoxification unit Exclusion criteria: none mentioned Pretreatment: no significant differences between groups in regard to: number of participants taking part in each session who volunteered to be research participants; total number of participants in each session; total number of times participants had been admitted to a substance abuse facility; age; gender; race/ethnicity; drug of choice. Confirmation of population eligibility (from study author): author confirmed that participants had diagnosis of SUD.
Interventions	Intervention characteristics MT + SC Description: educational MT session led by board‐certified music therapist using blues songwriting to address triggers and coping skills. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session Verbal therapy + SC Description: education without music consisting of a discussion of triggers and coping skills led by same 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 same therapist, with some discussion of songs, artists, and associated memories. Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session
Outcomes	Motivation to stay sober/clean – Likert‐type scale Outcome type: continuous outcome Reporting: partially reported Scale: 7‐point Likert‐type scale Range: 1–7 Direction: higher is better Data value: endpoint Notes: researcher developed 7‐point Likert‐type scale concerning motivation to reach and maintain sobriety. 1 represented "not motivated" and 7 represented "very motivated". Motivation for treatment – Likert‐type scale Outcome type: continuous outcome Reporting: partially reported Scale: 7‐point Likert‐type scale Range: 1–7 Direction: higher is better Data value: endpoint Notes: researcher‐developed 7‐point Likert‐type scale for treatment eagerness. 1 represents "not eager" and 7 represents "very eager" for treatment.
Identification	Sponsorship source: none Country: USA Setting: inpatient detoxification unit Author's name: Michael J Silverman Institution: University of Minnesota Declarations of interest: no conflicts of interest reported
Notes	Email (13 September 2017) from author confirmed that participants met criteria for SUD.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: participants in 15 sessions were cluster randomised into conditions by session. The numbers 1–15 were randomised into 3 groups and each group was assigned to a condition. Not otherwise specified.
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: missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups. Reasons for missing outcome data unlikely to be related to true outcome.
Selective reporting (reporting bias)	Low risk	Judgement comment: no selective outcome 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.