When you export a playlist from a music library app, such as iTunes, it exports it to an .m3u file. The head unit plays the songs in alphabetical order, so the app that reads the m3u file will rename the files by adding a number before the filename, so they are listed in the order in the playlist. I've been doing this for a long time, ever since there was a single DIN headunit that could read MP3's on a CD. Had a unit in my 1996 Outback, then my 2004. No need for my (whenver it arrives) '16 since it already supports USB drives. I have a SanDisk Cruzer ready to use in my '16.