Here's an audio format I would like to see for Rockbox: GSF (Gameboy Sound Format, if I'm not mistaken). The format is used in Game Boy Advance games. The way the format works is, it relies on one large file as a sort of "instrument database"; and it uses several small files - often less than 512 bytes - as the "sheet music".
The format appears to be very similar to the PSF (Playstation Sound Format) file type. With that said, I was only able to find one player for which the source is available, and said player is a Winamp plugin. The author's website for the plugin is
GSF Central , and the source is here:
http://www.caitsith2.com/gsf/player/in_gsf_src_0.11.rar .
So, if anyone has any interest in this format, please say so. I am a big fan of GBA music and I'd love to see this one go through.