The samples are looped accordingly to the spc information, most of them are tuned to a, if not, they're at least tuned to some note in the chromatic scale. Snare, bass drum and hi-hat are tuned the same as in most mmx2 songs (some songs differ slightly). The rest of the drum samples can be varied in tune, as they are also varied in mmx2.
These are all samples you can find in mmx2 spcs, some are not used ingame. For instance 32.wav is a cut version of 28.wav, but only 28.wav is used. I didn't take the time to sort them, they are mostly in the same order as in the spc, but this shouldn't be a problem.