This is NOT ready for inclusion in CVS, but if anyone wants to see the
mixer effects API we’ve been discussing in action, apply the attached
patch to the latest CVS of SDL_mixer.
When running playwave, you can use the -f option to flip the stereo
channels (This uses Mix_SetReverseStereo()). There’s also a #define in
playwave.c to enable a test of the panning effect, where the voice shifts
back and forth between speakers during playback (Mix_SetPanning()).
It’s kinda cool. 
As it stands now, the effects API itself is implemented (but not
necessarily debugged), and I’m just filling in the built-in effects
(reverb, etc are still forthcoming…).
To not spam the list anymore, I’ll refrain from posting any more patches
until I have a final product ready. In the meantime, feel free to email me
off the list if you want to get interrim updates.
Bug reports, comments, complaints, and well-endowed women named
"Cassandra" are, as usual, welcome.
–ryan. (@icculus)
[EDIT: patch deleted from Discourse. You can get it here: http://lists.libsdl.org/pipermail/sdl-libsdl.org/2001-June/018073.html ]