I like to do experiments. I'm trying to find a way to control multiples parameters like the frequency of an LFO or cut of a filter in real time. Of course i can do it in an easy way if i create a macro and assign it to a Midi Controller. The point is that, i would like to control these things while i'm using my theremin. For example as i move my hands near the antennas to modulate the volume or pitch of the sound i would to variate also the bandwith of a BPfilter with the same envelope that i'm creating with the movement of my hand. I know that probably this could sound weird...but i'm grateful to anyone that can help me with my weird ideas. Thank you.
You're in luck then as the CV (Control Voltage) outputs for pitch and volume on your Etherwave will allow you to do exactly that with the addition of some other gear.
You'll need to get some other CV capable equipment such as moogerfooger pedals or a modular synthesizer. Doing this will open a wonderful world of weird sounds and possibilities.
There is a whole universe of techniques and equipment available. More than could be answered here and much of it is a personal journey of what you decided you want to explore.
I strongly recommend you spend some time on the muffwiggler forum and watching the I Dream of Wires Documentary would also be a good starting point as it chronicles the recent resurgence of interest in modular synthesizers.