It is a subtractive synth, but instead of being fixed to standard saw, triangle, square waves the user is given a text box and they can type in any mathematical operation they like to create a waveform. The trick is these aren't 'real' functions in the mathematical sense where the output is directly calculated from the inputs. Instead, they have some internal smarts, so they are smart enough not to alias. (Not in every case, the basic cases, I'm sure you can break it and make some nasty sounds)
The basic functions are sine(x), saw(x), triangle(x), square(x) and pulse(x, pwm). You can then use these functions, add them together, multiply them with LFOs and macros, run them through filters. All sorts of wacky stuff.
The manual is here: https://gist.github.com/FigBug/a28da990 ... b62573f717

I have no idea if this is musically useful or just a nerdy experiment I wanted to try.
