University of Melbourne theses can be identified in the Library Catalogue. Limit your search to UNIVERSITY OF MELBOURNE THESES, and search by author or title. To view the full list of Music Therapy theses, use the keywords music therapy.
The full text of international Masters and PhD theses is available to University of Melbourne students and staff from ProQuest Dissertations and Theses Global. There is excellent coverage from 1997 (and selective coverage pre-1997).
The Finding Theses guide contains a lot of information on finding Australian and international theses.