What disorder is music therapy most commonly used to treat?

I am writing a Psych research paper and I am really intrigued by the idea of music therapy so I chose that for my topic. I would like to narrow it down a little more, though so I was wondering if anyone knows what it is most commonly used to treat? From the research I've done, I know that it has shown to be effective with depression, Austism, trauma victims, dementia, substance abuse, etc. Just wondering if anyone has any feedback on which of these disorders I could find the most information on...It is a fairly new method of therapy so the info is fairly limited and I am just trying to figure out what my best bet of filling a few pages would be. Thanks!