The fastest way I know of to do bulk file transfers (like an entire music library) is to take the SD card out of the phone.
Before you remove it, create a folder called music in the file manager app (if you don't have one already), dismount the card, then remove it.
Put it into a USB micro SD reader, plug it into your PC or Mac, and transfer away.
With a PC it is as simple as drag and drop after that. If your PC has a USB 3.0 port it should be pretty quick. Not sure how it works with a mac.