As a result of its low cost, tolerability and relatively good rates of compliance, there has been an increasing interest in music therapy as an alternative treatment for people with various mental illnesses. You’ll note that effectiveness isn’t mentioned in that list. Music therapy is defined as the:
professional use of music and its elements as an intervention in medical, educational, and everyday environments with individuals, groups, families, or communities seeking to optimise quality of life and improve physical, social, communicative, emotional, intellectual, and spiritual health.
This definition is from the World Federation of Music Therapy so it’s no surprise it has a list of claims it would take you all night long to read. Basically, music therapy involves people who are trained in it, using music to try to make people feel better.