Image via WikipediaCompendium of Sources for Music and the Autism Spectrum contains a nice bibliography for the effects of music and the autistic spectrum. There is a bibliography of music therapy, auditory integration therapy, entrainment, and pitch perception. You need access to paid databases to get the articles. However, this compendium does give you an idea of what topics are under serious consideration.
Music Therapy has been evaluated as a treatment that does work for autism. I think that it is not employed more often because insurance companies and conservative practitioners think that anything fun is foo-foo.