So you're looking for a beauty that encompasses technique, style of playing, personality, and the way they physically look? Or just how the person looks physically?
I don't know too many classical musicians, sadly. But I have seen and heard Elena Hammel and I have to agree she is quite striking. Tori Amos definitely wins some votes for me, in the popular music category. She's starting to age now <sigh> gracefully, however. Surprisingly well in fact. Truth be told, I think when a performer reaches a certain age (no particular number, but an age that is up there) he or she finds a golden era of performing due to all those years of experience.
Cyndi Lauper, the early years, is someone that strikes me as beautiful - more innocent than beautiful, perhaps, but still beautiful.