I would imagine that it would be possible to compose a selection that functions perfectly with respect to timing, intonation, and so forth, and yet have no "definition" or goal for the piece other than that it be technically precise.
I know a music therapist with an AS son my age who has been using her knowledge as a treatment for him. It helps him to concentrate, relax when stressed, and calm down when agitated or upset. I don't know if it has had any effect on his learning or other such things.
I know that I use music (though no kind of therapy) for much the same reasons. It seems to help.