If you use a Mac, and use iTunes, this has been a useful utility to migrate music to a USB stick (and/or) onto the internal hard drive of the Connected XL system.
It creates a complete folder/subfolder system and .M3U playlists that can be read by the MINI's built in audio system.
Some tips:
Create mutliple playlists in iTunes. Perhaps even a "Master List" that contains all the music you want.
Drag each playlist (one at a time) to m3unify. It will then "replace same-named files" if there are any duplicates
Be sure to "Generate an M3U playlist file". When you click save, give it some name, BUT DON'T FORGET THE M3U extension (or the mini won't see it). For example: My Happy Songs.m3u
Continue this process for other playlists until you've filled up your USB stick.
Plug it into the Mini, and enjoy!
You won't need to worry about iPod batteries draining, or always using Bluetooth. I now have about 2200 "256k AAC" files permanently on my mini.
It's great when Spotify is out of range, or I'm sick of what's on the radio.
(This utility is not free, but a minor charge $5 USD to use).