> Fully working Keyboardmania (although I suspect when it finally does work 100% and I > play it, I will discover that the song selection is all Korean crap I have never > heard of
You can find out the song selection right now. Run kbm2nd or 3rd, hit F2 when it errors out, restore factory settings, flash sound rom for a few minutes (it doesn't seem to end properly, so give it about 5 minutes of wall clock time at 100% or more speed and then quit MAME cleanly so the NVRAM saves). Restart MAME and the game and it should boot right up. (kbm2nd you may have to hold down the right arrow to avoid an error calibrating the controls).
This same procedure applies to all the ParaPara games in firebeat.c, by the way.