A great source for VG music is
Zophar.net's VG music archive.
Your program looks like everything I have ever longed for!!...
...on the GP32. Would you consider porting it?
Or since you seem to be releasing the source, someone else will hopefully do it if you don't.
This would be just so awesome, even if not all formats would work (because of the GP32 not being fast enough).
Arr, now I want my GP2X back. :-(
EDIT: I'm messing around with the Windows version now, very impressive! The playlist feature is great. Also, the sound quality on all formats I tried so far was very good.
I noticed that folders with non-ASCII characters don't get displayed correctly with the Windows version. Characters like à and so on get displayed as blanks.
Another thing you should consider adding is support for RAR compression, which is the de-facto standard for SPC and GYM/VGM soundtracks.
For example, the whole soundtrack of a SNES game is usually put in a RAR archive and then the extension is changed into .RSN . The compression is also better compared to ZIP.
And I always like to have the remaining time of the song displayed instead of the elapsed time.
Would it be possible to only add specific tracks from NSF/GBS files to the playlist? Because those files are always full of sound effects and other stuff you don't want to listen to.