FM on audio

What Lewis demonstrated is an example of ring modulation on an incoming audio signal. If you want to do frequency modulation on a live audio signal, it is a bit more involved than you might think.

First what you need is a way of pitch shifting the incoming signal in realtime. Whatever method you use for pitch shifting, you must be able to control the amount of pitch shift with your modulating oscillator (i.e. your pitch shifter must be able to receive control from a signal). One thing to look at would be modifying the [transposer] abstraction in the pitchshifting-playground example. That as well as some uses of variable rate delays on FFT are two methods for doing this that are on my list of experiments. I am probably going to mess with that later this month, but it will be a few weeks. When I get to it, I'll surely post my results.