Can mp3 (or any other non-MIDI) files actually be used as music in RPG Maker (XP/VX)?

I've been developing tunes for my friends RPG Maker games via GarageBand, and have wondered to myself if my work would actually play back. As a default I have them encoded in mp3 format. I've watched lots of YouTube videos and whatnot, but haven't seen anything yet that says the music can be non-General MIDI.