Now here is something I did not know about. The Rio Car review at MPeX.net states the following (translated from German by AltaVista's Babelfish):

"By coincidence we are encountered the possibility of playing also files in tar the format. Tar is a Komprimierungstool originating from the Unix area. Complete albums can be stored and played so compressed in one tar file on the RioCar. There the RioCar from a Linux system exists is obvious this support. Only restriction: Within " types of GET " of an album cannot be selected TRACKS, since the Tar file is treated as an individual TRACK."

I never knew this. You can tar-up an album and it'll play as if it were one track? Interesting. Do the song titles change at each track boundary or what? This is interesting.

Perhaps maybe it's simpler than I'm making it out to be. Maybe a TAR file is just all the files appended together with a bit of header data (which emplode would ignore), thus being the same as if I'd just done a copy /b track1.mp3 + track2.mp3 combined.mp3, in which case there's nothing special about the empeg, it's just a coincidence of the file format.