Thanks for the answer Deathbasket. I've only made custom music for Super Mario World before, and that was before the use of custom samples became widespread, so my knowledge of these things was both lacking and outdated. Anyway, that means no more reasons to procrastinate!
So let me get this straight, if I were to use FL Studio, this tool, mml2n64, and a OoT debug rom, I wouldn't need anything else to make custom music for the game? Or would I be missing tools?