I burned a bunch of music on a data cd (CD-R), i tried to play it in my 6 cd changer in my 2004 Volkswagen MK4... but when i press the button on which cd case it's on, all it says is CD-ROM, and than switches to #5. Why won't it play? is it compatibility or something?

PLEASE HELP ME!?

I've seen mp3 files work on data cds with MK3s.