Silverman 2021.

Study characteristics
Methods	Study design: cluster RCT Study grouping: parallel group Allocation concealment: method for allocation concealment not specified Randomisation method: throughout 22 total treatment sessions, the researcher cluster randomised participants into conditions by session using a computer program. Numbers 1–22 were randomised into 2 groups and each group was assigned to either the lyric analysis or control condition.
Participants	Baseline characteristics MT + SC Gender male: 37 (61%) Age: 39.34 years Sample size: 61 SC (wait‐list control) Gender male: 27 (40%) Age: 40.93 years Sample size: 67 Overall Gender male: 64 (50%) Age: 40.14 years Sample size: 128 Inclusion criteria: adults hospitalised on detoxification unit (and meeting criteria for SUD); able to read English Exclusion criteria: none mentioned Pretreatment: no statistically significant differences between groups at baseline for: ages; number of times admitted to a SUD rehabilitation/detoxification facility; number of service users taking part in each session who volunteered to be research participants; total number of service users in each session; gender; race; primary substance.
Interventions	Intervention characteristics MT + SC Description: MT group lyric analysis session addressing motivation and commitment to sobriety Session length: approximately 45 minutes Frequency: single session Duration of treatment: single session SC (wait‐list control) Description: wait‐list control Session length: not applicable Frequency: not applicable Duration of treatment: not applicable
Outcomes	Motivation for treatment/change (SOCRATES – Taking Steps subscale) Outcome type: continuous outcome Reporting: partially reported Range: 8–40 Direction: higher is better Data value: endpoint Notes: used shorter 19‐item version of SOCRATES, Taking Steps scale. Motivation for treatment/change (Recognition scale of SOCRATES) Outcome type: continuous outcome Reporting: partially reported Range: 7–35 Direction: higher is better Data value: endpoint Notes: from short 19‐item version of SOCRATES Motivation to stay clean/sober (CSS) Outcome type: continuous outcome Reporting: partially reported Range: 5–30 Direction: higher is better Data value: endpoint
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: School of Music, University of Minnesota, Minneapolis, Minnesota, USA Declarations of interest: no conflicts of interest reported.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Judgement comment: participants in 22 sessions were cluster randomised via a computer program into conditions by session. The numbers 1–22 were randomised into 2 groups and each group was assigned to either the lyric analysis or control condition.
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.