USB stereo connection, where does it search?

[azminisk8r]

Im trying to switch to usb for using my DX in my car so theres only 1 cable running to the car dock, but it seems my stereo is stupid, and searching in the wrong place.

Im running a very stereotypical sony xplod deck, does anyone know where this deck searches for music files? Or where do you keep your guys's music files? currently it cant find anything under /sdcard/Music where my 700 songs are but its pulling a few random files from idk where.