Use Winamp or your favorite media player to convert your MP3 music into WAV. In
winamp, for example use the DiskWriter plugin. Then use Audacity or Cool Edit
to split the stereo WAV(s) that you now have into 2 each of mono wavs with 
left and right channels...

THIS NEXT STEP IS IMPORTANT:
To get it so the proper channels go in the correct places and you have the 
correct track order, name each song as follows.

Original WAV song:	Split WAVs:
CD Track One.wav		01LCD Track One.wav
				01RCD Track One.wav
CD Track Two.wav		02LCD Track Two.wav
				02RCD Track Two.wav
CD Track Three.wav		03LCD Track Three.wav
				03RCD Track Three.wav

Where Track One/Track Two...etc is the name of the song.

STILL IMPORTANT:
Save the album cover as 000cover.bmp in the wavs folder.
It needs to be 100x100 pixels in size and 24 bit color uncompressed.
The BMPs made by Gimp work just fine.

Save the split wavs in the "wavs" folder, then double-click Go.bat if your PC 
is a Windows PC, or run go.sh in a terminal if you're running Linux.

You will now end up with a GSM.GBA file which has stereo music on it. Run this 
on GpSP or a real GBA. (It sounds pretty broken-up in VisualBoy Advance CE.)
