I'd have more respect for someone who is a musician if they canceled their performance rather than rely on Lip Synching if they were having problems. There's a long list of 70's and 80's rock bands who have cancelled performances because the lead singer has a sore throat, etc.

Also, if you have to lip synch because you can't gyrate around on stage and sing at the same time, HIRE SOME BACKUP DANCERS. When I pay to go to a live performance, I want just that, a live performance. If I want to listen to lip synching, I'll just go listen to a cover band.