Custom music

There are some MP3 to midi converters out there, I've never had any luck with them either though and cannot even refer you to one. Converting an MP3 to midi would most likely result in a ton of notes all over the place, though maybe if it's a good converter it could separate the notes to go on different tracks, but still that's the main problem with an MP3 to midi conversion for music hacking purposes, as we can only have up to 8 channels and can't have notes playing all over each other (chords). So if possible try and find a midi file of the song.

Firstly, have you taken a look at either of the music hacking tutorials?