Can anyone figure out this (David Tudor) circuit?
Take a look at http://en.wikipedia.org/wiki/RC_circuit under the Parallel circuit section.

That circuit allows you to adjust the resistance (with a pot) and adjust the capacitance by opening or closing switches. So, you can have any combination of switches open or closed to get a different effective capacitance.

The capacitor between Black and Red is just always added with the switched capacitors.

The pot and capacitor at the end is a Snubber, find more info at http://en.wikipedia.org/wiki/Snubber