I'm just putting this here for anyone else looking for a solution for the same problem.

I have a 2014 S4 and I was kind of ticked off to learn that Audi's MMI doesn't recognize the "album artist" tag on music files. While the iPod cable included with the car works, the "Artist" list then includes every artist on each individual track, which for me is completely unwieldy. Plus the included cable doesn't pass through album art.

My music collection dates back to MP3 players that required a very clean file folder folder structure (Album Artist/Album/Track (with track number as the first part of the track name), and I have kept that up. For $13 I bought this MMI/USB cable off Amazon: http://www.amazon.com/Audi-Music-Int.../dp/B009ZC7VQU . I used Synctoy to copy my music collection to a portable hard drive I had sitting around and just plugged it in.

It works perfectly. I didn't have to reformat the drive to FAT32 or undertake any of the other gymnastics I have seen reported online. The MMI reads the file names so I can access my music the way I want, and the "now playing" popup reads the tags and passes through the album art in the tags.