Today I finished making my RSynth. This is a resistance-based synthesizer, based on a large variable resistor and a VCO circuit.
Here's another view:
It's made from a piece of plywood with a large amount of conductive paint, a steel wire with tensioner, a copper wire with tensioner, and a 555 Timer-based VCO circuit, which, by the way, is extremely easy to build, and versatile, accepting power from 5-15 VDC.
And now for a video: