Unfortunately, I know very little about Tourette's, having known only known one person who had it, and read only a little. What follows is only speculation. (I must say, I smelled a "troll" when I first read your message, but will ignore that possiblility.)

The nonsense syllables in folk songs (if I understand correctly, the "diddly-aye-duram-dinkums") are probably more difficult to sing than words that have meaning. Maybe you meant "whoopin' and a-hollerin'?" I'm not sure what you mean by "involuntary body movements." Foot tapping? Rocking ("chair dancing")? The urge to stick one's finger in one's ear when singing without accompaniment?

It would help if you gave some examples of what you meant by involuntary body movements and random, incoherent mouth noises in relationship to folk music.

If it's true that nervousness can exacerbate Tourette's, then any music that has a calming effect, or draws a person into it, would help. Everybody does what people with Tourettes do. People who don't have Tourette's can usually stop whenever they want. If you're suggesting that some folks with Tourette's started the noises and movements way-back-when, and others copied them...anything's possible.

Mary, I'd be interested on the article you mentioned, but not if it's too much trouble.