It doesn't entirely make sense to me from the female point of view, but from the male point of view being artistic (in this case musical) makes a lot of sense in Darwinian terms!
thing is, I don't even buy that musicians' popularity with the opposite sex is a universal thing. For most of history in China (where I live) - if you want to have a random sample of humanity and culture, can't quite ignore China can you - being a musician is quite a lowly occupation. it's only in the last 50 years when they began to make big money that they became desirable as sexual partners.
evolutionary biology no doubt determines what we look for in a mate. but it's not as fixated on some notion of beauty as pure reproductive advantage.