Lkeller said:I don't know about musicians, but it's my understanding that if you're registered as an actor with AFTRA, you cannot use a name for professional purposes (even your own birth name) if it is already being used by another AFTRA member. Hence Michael J. Fox, and Terrence O'Quinn. There are numerous other examples.
It's also true with British Equity. One infamous case was a British actor who was born as James Stewart - but because of the U.S. actor Jimmy Stewart, when this British actor started making movies in the States, he had to adopt the name Stewart Granger.