An excellent tracker and player for GBA is the "GAX sound engine", made by the guys from Shin'en
. Shin'en did not only create some excellent GBA and DS games, the GAX sound engine was also licensed by many other developers in used in tons of GBA games. It now exists in a highly modified version for DS and I think also Wii.
The GAX sound engine is a follow up to AHX on Amiga
(formerly known as THX
), which was created by the Amiga demogroup Abyss and was written by Manfred "Pink" Linzner, who's also well known for his great tunes. Maybe they're offering their old (and now no longer used) GAX engine for free to such a famous musician like you Ray. Like most of us the guys from Shin'en grew up with the games for which you've made high quality soundtracks.