I imported some CD's to iTunes, copied them fom My Music to a USB drive than plugs into the head unit in my car. On some (not all) there are an equal number of tracks following the actual songs (i.e. 1-12 play fine, 13-24 show as unsupported format) that seem to be "extra". when I plug the USB nto the iMac and look at the folders I don't see anything other than the actual tracks in .m4a, which sho as AAC on my head unit. Any idea what these are and how I can et rid of them?