As written I would score this essay a 4 or 4.5. The essay has a clear structure but the paragraphs read as a list of assumptions, rather than an analysis. If you had stuck to one main problem and then explained the ramifications of that problem the essay would have been clearer. For example if you has said something along the lines of if music therapy was found only to have a calming effect in the most severe of cases, this would damage the author's argument because it would show that the treatment he suggests is not one that can help people before they advance to major symptoms.
Also, your essay has some small style issues such as using and also that could be fixed upon proofreading. Overall a solid effort.