Audio Filter FFT

I would like to learn something about the fast fourier transform, in particular it would be nice to look at some code for a dsPIC33F. All I have managed to dig up so far starts straight in with math that would make Uncle Albert think a bit, and my understanding stops short of the calculus.
As a first thing to play with, I have a project for disco lighting which would need a spectrum analyser type output, and it would be nice to know what I could expect in terms of number of channels, repetition rate, etc.
Can anyone point me in a direction, maybe not even the right one?

If you check the PICList there's an OLD project creating an audio spectrum analyser using (I think?) a 17 series PIC, and it even drives a VGA monitor directly.

It should be fairly 'easy' to convert to what you want.

Maths wise though, FFT is VERY complicated!.