I can offer one datapoint of anecdotal evidence. My mother plays and teaches recorder in Florida. One of her studens is a young adult with Tourette's. Playing music seems to have a beneficial effect on his condition. For some reason, it doesn't surprise me. Singing can help stutterers. I don't know if there's a connection there or not, I'm just rambling. I'll be interested to see what other people's experiences are.

jeffp