He apparently suffered from something called "Spasmodic Dysphonia" (unable to speak normally) for the last year and a half, but appears to be recovering. His story is here:
Based on his description of what happened to him, I'm inclined to think it's a TMS variant. He couldn't speak in normal conversations, but he could speak in front of crowds, and he could also sing. Talk amongst yourselves
Wow, this is uncanny! I've never considered this. Reading the post, it does sound very much like TMS. The coming and going symptoms. Definitely worth the read! Thanks for the link!
I believe it is TMS. It's like the "yips" -- a term used to describe golfers who choke on short putts. I believe a famous concert pianist also came down with a case of the "yips" where he could no longer play the piano.