
first thing i do when i get a game is hacking it.
what you need:
wwf raw on hdd or rewrite to dvd-rw/cd-rw
mp3 to wav converter (google)
dreamcast movie maker (google)
what you do:
ftp to your xbox and get into the raw folder.now go to adx\bgm\
here are the music files.for this example i'll use mu_albert.adx
this is alberts entrance sound.
make a backup of your files before replacing them.
1. get a mp3 file that you like and convert it to wav.if you have already a wav file it'll be fine also.
2. start dreamcast movie maker and uncheck "use identical files"
3. click the select button in the audio window and search for your wav file.
4. set the type to sofdec audio (.sfa) and give a output filename
5. start encoding
it'll take some seconds.
now rename the finished file from yourname.sfa to mu_albert.adx and overwrite the one in the adx\bgm folder.
if you select alberts music in the game your file will play.
hope you'll enjoy it

that can be done for every file.i just used mu_albert.adx as example.