I’ve been thinking about building a harmonigraph once I have room for it, but in the meanwhile a simulation will have to suffice.
This one is made with the parametric equations
x = sin (A t) + sin (B t)
y = sin (C t)
It still needs tweaking, but you can get some cool looking stuff. You get a new configuration by clicking twice (the first click sets A and B by looking at your mouse’s x and y position; the second click sets C as the mouse’s x position).