Need advice on replacing Theremin for interactive sculpture

Hi!

I have a Theremin in a sculpture that requires frequent tuning of the variable capacitor on the circuit board depending on the temperature, humidity, nearby objects, etc. and it's virtually impossible to have it work in an exhibition for more than one day before it needs retuning.  The Theremins were built back in 2001 by a friend, and I'm wondering if there are any replacement options these days for a Theremin that needs no retuning on the board (or automatically adjust), and can be fine-tuned as needed with just one potientiometer or whatever to make it easy on the gallery sitter? I can't really go to the gallery every day to get up inside the sculptures to do it, and it's impractical to ask the gallery sitter to do so.

I only need pitch, and it has to be sensitive enough to have the lowest pitch begin about 3-4 feet away from the sculpture. The most octaves possible would also be an advantage. Currently, when the viewer is 4 feet away, the pitch is very low and the floor rumbles, which is a function I'd like to preserve.

You can see the sculpture(s) in action here (sorry the movies only work on Mac):

http://www.SATResearch.com

Just click on the "function" link and there are movies on some of them. Some browsers won't play QuickTime, so you'll have to right click and "download link" to watch them, sorry.  Really need to update that!

Thanks!
Satre

Preserving the low pitch at a particular range sounds like a job for a digital theremin that has an automatic calibration function.  All theremins drift around to some extent and the place where that drift is most noticeable is at the physical location of the zero-beat (that would be very close to where you start hearing the sound).

Even a typical analog theremin should only require a single knob adjustment at any time to set this threshold (don't know what you are using now), although just being close enough to the theremin to adjust it would mean that you would need to tune to a particular note instead of a zero-beat, so that when you back out to 3-4 feet the note drops to zero.

A digital theremin would allow you to put a calibration switch at a fixed location so that as long as the gallery sitter is the only person in the vicinity all they would have to do is push the button and the theremin would revert to the exact conditions that you want.  That button could just as easily be right on the theremin itself.

I know of one circuit that would for certain do exactly as you want assuming that you have a reasonably conventional antenna, and that would be the D-Lev by Dewster right here on Theremin World.  Assuming this is a pitch-only display (no volume control by the user), this would be a pretty simple low/no maintenance setup (except for the occasional button push). Plus you could alter the sounds and sound effects if you wanted - a lot!  Send a personal message to Dewster or me if you like and we could possibly help you out with something.

Another inexpensive theremin that might do the job is called the "open theremin", although I haven't played with that enough to remember how it works.

Thanks! I have no idea why the font is so huge in my original post. Sorry about that!
This would have to be something ready-made, as I'm running out of time for building from scratch. (Not to mention all the variables my soldering skills would introduce ). Also will have to work from a power supply as we won't be able to easily change batteries. Sorry I forgot to mention that above.

The antennae are large, seen in the pictures on the web sites. Not sure if that makes a difference. They are connected to the Theremin by shielded RF cable.

I don't see a specific sculpture that you are referring to, so I can't see the antennae (do you have more than one?).  Can you post a specific link or a picture?

Also, running through coax isn't going to work with most theremins.  The electronics, or at least the critical part needs to be right at the antenna.

http://satre.org/SATResearch/pages/olive.html

http://satre.org/SATResearch/pages/needle.html

http://satre.org/SATResearch/pages/horn.html

If you click on the "function" link right under the rendering, you will get to a page that has pictures and movies of the pieces in action. The pieces with two antennae have both hooked up to the pitch.

Thank you!

Hi satre! Welcome here. The sculptures are really amazing. What a nice idea! Do you mind give us the circuit of the pitch theremin used? 

Nice sculptures indeed! So do you have a separate theremin for each display or are you somehow sharing one?

Thanks! Each sculpture has its own Theremin inside. I did not build the Theremins themselves, I only built the sculptures and antennae, etc. The Theremins were kits put together by a friend of mine in 2001. I do not recall which kit but he said they were about the highest quality available at the time aside from Moog and as I recall, they cost around US$100-150 for each kit. There are two potentiometers for coarse adjustments that I have to use plastic tools with, and there are knob potentiometers for fine tuning. The kit had both volume and pitch circuits, but I only use the pitch. The output is a 1/4" jack which I feed into a small but very powerful Roland amplified speaker.

I wouldn't be surprised if it was a Harrison Instruments Theremin because my friend lived near their factory and I think I remember him saying the kits were from Maryland, USA, but I could be totally wrong. I will try to stick my head up inside one of the sculptures tonight and see if I can find any identifying information.

I was able to get my phone up inside and take some pics of the Theremin in there. You'll notice that the aluminum cover is cut open -- which allowed me to do more coarse tuning easier. Let me know if you recognize this kit. It works extremely well, just drifts a lot with temp/humidity (I know that's normal, just trying to find a more suitable alternative since I won't be there to do the tuning every day).