There is a way to rip certain music from a small selection of games. It involved ripping the raw files from the rom then converting then to a usable format, Triforce was messing about with this about a year ago. Unfortunately some roms do not contain the music in a usable format and I am unaware of whether Digimon is one of these or not.

Check this post out here:

http://d.hatena.ne.jp/loveemu/20060114

I think this is where it all started