Just for fun, I'd like to program a little software synthesizer in SDL or SDLmixer. Mainly I'd like to program an oscillator class which you can specify a waveform for and envelopes, then you can program "notes" which specify a frequency and amplitude multiplier, as well as a duration.

So far I only see how to load and playback audio files with these libraries. Do they have any capacity for procedural sound?

I don't know about SLD_Mixer, but I think it has the ability to play midi files. Maybe you can somehow use that functionality to create procedural sound.

Here are a number of posts I've replied to in the past:

http://www.gamedev.net/community/forums/topic.asp?topic_id=255007
http://www.gamedev.net/community/forums/topic.asp?topic_id=196272

With another overview:

http://www.gamedev.net/community/forums/topic.asp?topic_id=187128

You are responsible for creating and managing the oscillator, and generating the output yourself. You could look at CSound and other software synths to get examples of how to create these oscillators.

Edit: It has been on my list of things to do to create a simple sample toolkit. Maybe this fall.

Thanks, Sphet. That helps a bit. It looks like, in SDL, the secret might be to manually edit the sound buffers.