Last month we saw Sarah Angliss using the Theremin as an audiovisual controller. If you’ve got a Theremin and want to try this yourself — or try some other similar continuous input — here’s a really simple example of a patch that converts audio to MIDI. It uses Pd, Max/MSP’s open-source cousin for Mac, Windows, and Linux.

If you haven’t used Pd before, you should download pd-extended. It’s a stable, friendly installer for Pd with all the documentation and extras you’d need. Pd can be tricky to install, but this is friendly to just about anyone.
Pure Data Downloads (choose “most recent release” for the latest stable build of pd-extended)

In this case, Charles Martin, a percussionist from Australia, whipped up this simple patch and the fiddle~ object (which analyzes incoming pitch) to control effects in Ableton. Very cool stuff. He describes the patch and includes copy-and-paste code here, though I actually recommend going through the image above one step at a time and recreating it to better understand what it involves.

Theremin to MIDI Control program in Pd [Charles Martin Percussionist Blog]