I'm not convinced that these were test tracks, since they're in slots smack dab in the middle of used Book 2 tracks.
Enter any map, then use an emulator's cheat function to set 7E0876 to whatever the slot number of the song is (they're in the filenames of the recordings I made). The game will start slowing down and acting weird, so then set 7E0877 to 00, and it will begin playing the new song. This works for almost any song, but a lot of slots seem to be duplicates, some blanks, and a couple things do get a little glitchy--a few Book 2 songs sound a bit weird if you make them play in Book 1, and the Book 2 epilogue theme never progresses beyond the first section. There's probably a better way to access all this stuff, but I'm far from a hacking expert, I just mess around with stuff and see what happens.