We had to talk a guitar teacher into taking on our DD at 6, and we mentioned her intellectual abilities as an argument in her favor. He'd never had a student that young. She learned very quickly. Unfortunately, she didn't have the discipline to practice or tolerate failure, and she ended up dropping it after several months. The maturity factor wasn't there yet. There's plenty of time yet for her to pick it up again later, and I'm sure she will.

My personal thought is that music naturally lends itself to the visual-spatial mind, because of the way it's written (the symbols are largely visual), the way it employs patterns, and the way it's underpinned by mathematical constructs.