By the way, as a music student myself, I just want to add that I happen to agree, 'musician' usually applies to someone who plays an musical instrument, an instrument being a tool created for doing something, so not the voice. I mean it's not something I would get really militant over, almost all really good vocalists at minimum dabble in some instrumentation anyway, but usually I only refer to someone as a musician if their primary talent is playing a musical instrument. I wouldn't refer to myself as a musician because I'm really only talented at composing and I feel like it would come across sounding like I can play a musical instrument well when I can't.
On the other hand, musician is the best catch-all term for whatever someone does when I don't feel like specifying.
Oh, and Amy Winehouse. She had more musical talent than a lot of people give her credit for I think. I think some of her songs were okay. That's all I have to say about that one really.