@ Assertn:
If you can accept the voodoo fruit, which involves not only perfoming it but producing voodoo figurines from your body, then I don't see why you can't explain the music fruit by that same 'logic'. He transforms his body into something that can be used to manipulate a natural phenomena (sound, in this case) much like Hawkins' ability to transform his body into a voodoo dolls that can be used to manipulate supernatural phenomena.
If you are willing the stretch the definition of 'natural phenomena' that much, then what's the problem? :P