These activities use an Arduino sketch called TinFoilTheremin available within the repository.
If you're already familiar with the Arduino platform and have a Touch Board, you can download the sketch from the green link above (or click here to grab the entire .zip file). You will also need to install the Bare Conductive package, available here.
Everyone else: please watch this space for better instructions! I'm in the process of uploading about ten years of work to GitHub, and it's taking time ;)
Symbols from instrumentmaker.org/instrument-maker-symbols