Thoughts on multiple-player/user effects possibilities?

[jaapie]

Over the past few months I've fallen down the rabbit hole that is the online diy synth community while playing around with guitar synth ideas. Although the circuits are more complex, the possibilities for real-time "knob tweaking" get much more interesting. Last night I was trying to come up with ideas for a christmas gift for a former bandmate. When we played together, the whole band had a lot of fun experimenting with "interacting" with each other's instruments-- tweaking knobs in real time on each others' amps and pedals or trying to "share" instruments between two people at the same time. He's recently been playing with a group of friends in informal, experimental-style improv jams and the thought occured to me that it might be interesting to build a box intended to make it easier to share playing "duties" between two people. In my head, it seems more intuitive for the person playing the guitar to control the pitch and volume of the shared instrument while the person manning the "box" would shape the timbre. Obviously, that doesn't have to be the case and a lot of fun could also be had switching things up in different ways.

In its simplest form, I was thinking of a box with a couple of theremin-style antennas(antennae?). One antenna could control an resonant filter's cutoff frequency, while the other might control the speed of an LFO modulating volume or pitch, or maybe the carrier frequency of a ring modulator.

I'm wondering if anyone has any experience or thoughts on this sort of project-- what sort of effects or other parameters would be interesting or fun to make externally "playable?"

[timd]

While not a theremin, you could try this build:

http://www.diystompboxes.com/smfforum/index.php?topic=99110.msg868143#msg868143

One person plays the guitar, one or more on the dials!