Ouch, not asking much are ya!
The only DLL I can think off would be FMOD, but that's probably platform specific. Really, I think your only hope would be to adapt an existing sound plugin somehow.
Personally, I would cheat. Like use pre-rendered images of the sound wave. You have to consider how you'd draw the sound wave anyway, maybe using the scissor command, which would be slow. Having the music or sounds as pre-rendered images might save a lot of performance. You could also have a low resolution data stream of the music, like use FMOD or something to record the volume every, say 10th of a second as a byte value, then a 4min music track would take up... 2,400 bytes, you could even interpolate to make it nice and smooth. This might be good for a volume meter. You could even chop that byte in half, giving 4 bits to each channel, like 2 sets of 16 LED's to represent the volume for example, and it would take very little processor time... maybe just have an animated sprite for the lights for super-quickness... so that byte data is actually representing the frame numbers.
I got a fever, and the only prescription, is more memes.
