hi transientlx,
i built that midi theremin but i'd guess it's not really what you need, it works as a gestural controller ok, but is rather limited in its scope unless you are prepared to make some significant modifications.
see this thread for more http://www.thereminworld.com/forum.asp?cmd=p&T=1047&F=715
in fact i was just talking with a guy who designs and builds hardware-software solutions about midi theremin as there seems to be a lack of decent solutions. maybe inthe future something more will come, but i'd say the jaycar kit as it stands is a fun project to build and capable of wild (read unpredictable) results - which i quite like, but when i want to play musicaly i use my kees enkelaar.
hope this helps, for what you need perhaps look at a Paia Theremax (http://www.paia.com/theremax.htm) combined with a Paia MIDI Brain (http://www.paia.com/midibrn.htm), or doepfer (http://www.doepfer.de/home_e.htm) make modules for building all manner of things, very good, solid construction. you can find a theremin antennae module which outputs cv, or a light sensitive one and so on - you'd need one per parameter, if you connect them to their cv to midi module you'd have yourself a controller that could be used with a range of midi gear, you should read their pdf manuals to see if that's viable for what you wish to do though. if i were doing this sort of thing live, i'd go with doefper just for the construction - my jaycar midi theremin wouldn't stand up to it i fear.
regards
