Hi, not sure where everyone else got started in building real time systems, but most of my experience comes from Max/MSP. Although the core of it is audio / midi processing you can use anything as a controller for anything else. I got really used to being able to stick a low frequency sine wave on a parameter to modulate it, but in processing it's not that simple.

In short, I made a simple translation between desired frequency and frame rate, in the form of an increment value.

Check it out:
http://www.openprocessing.org/visuals/?visualID=1074