I have been working on a circuit i call 'onehander'. The idea is to have a linear, one dimensional parameter space (for example, a potentiometer) that someone can play with one hand. And although this simple parameter space changes only one parameter (in the case of this breadboarded example, the speed of a control oscillator), the amount of variety in the audio output of the circuit is relatively large.
You can listen to a direct-input recording here. Please note that the audio has not been edited and has been recorded in a single, continuous take changing only the potentiometer. You can also watch a video of the thing in action here.
You can see a schematic here. Choose values from 22kΩ and above for R2 - R16.