I can't remember how to convert an MP3 file into a sort of module that JJ2 could use. What program would allow me to do that? (I'm well aware that there's a loss of quality, and I'm hoping that it just removes the lyrics instead of making the whole song sound bad)

this one

Ok, how about MP3 to MIDI or something like that without making it sound like it's only using one instrument?

Impossible, if you know anything about how the formats work. Midi stores notes, MP3 stores soundwaves. Midi doesn't use samples, so you can't put said soundwaves into a midi. Also, using the search function or google before asking probably would've given you the same answer.

Well I remember converting an old song into a format and there was a change in the song, but it didn't sound like it was only using a single instrument. I don't understand what happened, but I did like the results.