My voice definitely changes according to my level of l-dopa in my system. Guess I do my own therapy...sing as much as I can.When low in l-dopa, voice is lower pitch and cracks when I sing...sounds lousy. When l-dopa is a good level and I am not under any stress to perform, my voice goes back to where it was in 7th grade before my diving acccident..a very nice tone/ relaxed and a higher range. Humming at times seems to help . Making very loud Lion-type yawns. Also patting face and massaging face and neck to try to keep muscles more functional...lots of neck stretching. Got to keep everything mobile.