Corbett 2008.

Methods	Randomised controlled trial (cross‐over)
Participants	Diagnosis: autistic disorder based on DSM‐IV criteria, Autism Diagnostic Observation Schedule‐Generic (ADOS‐G) and clinical judgement Age: 3‐7 years n=11
Interventions	1. Tomatis Method: filtered music, "Electronic Ear" headphone, auditory feedback, specially produced compact discs of Mozart and Gregorian chants 4 three‐week treatment blocks, total duration: 18 weeks 2. Placebo: commercially produced Mozart and Gregorian chant compact discs, no active microphone or "Electronic Ear", schedule as for treatment group
Outcomes	Standardised tests assessing core features of autism, cognitive ability and language
Notes	No loss to follow‐up
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sequence generation table provided by a independent statistician (personal communication with study author)
Allocation concealment (selection bias)	Low risk	Sequence table held in a sealed envelope in locked filing cabinet until study completion
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up
Selective reporting (reporting bias)	Low risk	The outcomes listed in the methods are reported in the results
Other bias	High risk	The authors report that "although the participants were randomly assigned to the groups, the developmental level appeared to be different for each in that the placebo/treatment group was higher functioning than the treatment/placebo group." The study was a crossover design and it is unclear whether there was sufficient washout between each treatment period
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Parents blinded until conclusion of the study. Individuals administering the music were not blinded but were not affiliated with the M.I.N.D. institute (Corbett 2011)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	M.I.N.D. institute researchers remained blind until the conclusion of the study