There used to be an alternative iPhone management tool created by some of the same developers who were jailbreaking iOS. Certain features only worked with jailbroken phones - but you could still manage your music library even on unmodified devices.

It's been a few years and I'm not sure if its still in development. I believe it was called iFunbox? On mobile now and don't have the opportunity to search for more info - I will edit this later.