I had the same problem. My first attempt was to export the waveforms from a
free SBLive soundfont, but those are intended to be looped, and the GBA
won't loop them, at least not with the Nintendo music library.

I ended up creating a MIDI file that played C5 over and over again with
patch changes in between, then played it back and sampled it on a
full-duplex sound card. Once the individual samples were isolated, filtered,
and downsampled, the results sounded pretty good.

The only problem is that with one-shot samples, the sample needs to be at
least as long as the note to be played, and the effective length of the
sample gets cut in half with each higher octave, so if you have a lot of
sustained high notes, you'll need very long samples.

I've never used the CGB-compatible waveforms, so I'm not sure how people
come up with those, but I'd guess that the majority of GBA games are using
direct sound.

- Mike

> Since the GBA doesn't have built-in patches for General MIDI etc, how do
> people go about getting MIDI files to sound good on the GBA? If your
sound
> department generates a MIDI file, how do you generate the corresponding
> patch bank to use the CGB-compatible synth?
>
> Thanks!
> Rebecca
>