Kim is absolutely right about what works for one may not for another - that is why, when you start doing music therapy with someone you need to do an assessment. (And we use it for physiological processes as well as mental ones - rhythmic breathing to help with respiratory problems, music to enhance the rhythmicity of physical therapy exercises, etc.)
If someone tried to do music therapy on me with hardcore, twangy, nasal CW, for example - no way would that relax me - just annoy, resulting in no therapeutic effects. But there's a ton of music I love that I know others hate - skirling pipes, etc! GOTTA do an assessment to find out what they find relaxing, stimulating, etc.
Then you have to go with what they want - living in small town Iowa, it is, often, the exact music I hate, but I have to use it without betraying my own prejudices. This can be DIFFICULT! *BG*