It's not just nervousness--there are people who truly sweat excessively. Usually those folks have the problem in a lot of different settings. If it's just when a person feels obviously nervous that's different. Drysol is the standard medical recommendation. I would only consider surgery if music was your career. It's not a big operation--the nerves are in the chest and are accessed with a small scope, not a big incision. But you lose the ability to sweat on the upper half of your body if both sides are done so makes exercising a problem (but we all know professional musicians don't exericse. It would interfere with your ability to thrash around on stage.) If too much nerve is removed the eyelid on that side can sag.