Pokemon Box uses MIDI with a 'soundfont' by jurassicPieter at 4:12 AM EDT on April 9, 2007
I was just looking through all the cube iso's i have to see if I can extract music and well I already knew you can load the pcm files but they only contain instruments(load the PCM-files in goldwave RAW, signed, 16 bit, big endian mono). So let's look where the sequenced data is. By extracting se_ram.arc I found out the game uses plain midi(and I can just load the midi's in any player) and every midi has a wt-file next to it which probably contains pointers to the instruments in the pcm file.
Here an example of what I found in the rom http://www.sendspace.com/file/7lql50
I know Pokemon Box is not the best 'game' to get teh music from but it's a start on playing sequenced data for the cube:P edited 4:12 AM EDT April 9, 2007