Korg MS-10 Theremin????

I have a really beat-up Korg MS-10 that is missing the keyboard and side panels. However all the electronics work and I was wondering what it would take to build a theremin controller into it. I definitely want antennas and not photocells. I'd also like to have both volume and pitch control.
Should I be converting pitch to cv and patching into the cv-in? How could a volume control be accomplished? Is there an existing make and model of theremin that would work well to modify and stick in there? I just started looking into this and any points in the right direction would be much appreciated.
Thanks!

I've done this with my MS-20. I should warn you that it sounded like goat sputum.

I think it is worth trying a theremin-like midi controller (I suppose that the Korg has a midi input...).

Such controllers are sold on German ebay or you wait still some weeks until FredM will have finished his more sophisticated construction.

Thanks guys!
It only has cv and no midi, so I was trying to think of novel ways to get it out of the closet and back into the system that don't involve buying a $250 midi-cv converter.
I wonder if one of these would work:
http://www.analoguesystems.co.uk/modules/rs30.htm
Or would I just have useless goat sputum that I could "control" with a theremin or any other monophonic source?
Maybe I should I try to build a cheap ribbon controller first to get familiar with how it responds to cv.

I Think the MS10 requires (unusually) an exponential control voltage - its CV is V/Hz rather than V/Octave - If this is the case, you will find that an exponential control voltage is required from your Theremin..

It works like this.. Most VC synths take a linear CV (Volts/Octave) and each module in the synth has an exponential converter to convert this to give musical interval relationship.. The advantage of this scheme is that each module can have a summing amplifier, and voltage(s) can be added to provide independent pitch/frequency control which will continue to track.. For example, one oscillator could have 1V added, and this will increase its frequency by 1 octave - and this shift will stay at 1 octave regardless of what is coming from the keyboard. Adding a fixed 1V to a V/Hz system will shift the frequency, BUT - This pitch shift will NOT stay musical - for example, lets say 1V was coming from the keyboard, and 1V was added to an oscillator, and this added voltage shifted the oscillator by an interval - as the voltage from the keyboard changed, the interval would change, and the module would go out-of-tune with other modules.

Control voltage from a Theremin (like the EW) are based on taking the audio frequency, converting this to a voltage or current (which will be a direct representation of the input frequency, and therefore exponential, or V/Hz) and then converting this to linear (V/Octave) so that it can drive conventional (1V/Octave) analogue synths.

It is easy enough to tap the voltage before the log converter to provide a V/Hz output - but it would either mean modifying the circuit, or getting a special build.

At this time, I have a board on my bench undergoing development and testing - this board is designed to take Audio (from Theremin or other monophonic signal) and give 1V/octave CV out, and Envelope out - It should track 10 octaves accurately, and uses (what I think may be)a new way of doing things.. Modifying the code to give a V/Hz output should be easy (in fact, I may now add this as a selectable option) - BUT - It could be a while before I can ship these (some people at TW have been waiting months for free evaluation samples and theremins I thought I was nearly ready to build) -

This board is an essential part of my Theremin products, so I hope to have it as pre-production prototype before September - But it may be 6 months or more before they are available. (I hope it will be sooner - but everything takes longer than I expected, and I now fear that I have been falsely raising peoples expectations regarding the launch of my products)

[i]"Maybe I should I try to build a cheap ribbon controller first to get familiar with how it responds to cv."[/i]

For the reasons given in my last, a linear controller of any kind will not give you a "linear" relationship - the space between semitones and octaves on your controller will be exponential..

Lets say you got 1 octave for the first 10cm, the next octave would be 5cm, the next 2.5cm etc.. The interval between each semitone will also be exponential .. relating to each other by the relationship 1/12*Sqrt(2)

You will need to follow any linear controller with an exponential converter to make the controller track equally spaced musical intervals.

Perhaps this is why others have found control of MS Synths less than satisfactory!

I have just confirmed MS10 CV is V/Hz..

[b]LINK TO MS10 SCHEMATICS:[/b]
MS10_Service_Manual.pdf (http://oldschoolsound.free.fr/manuels/ms10.pdf)

Wow, really amazing stuff Fred, thank you for all the info. Very inspiring.
Now my plan is to take an old suitcase tube reel to reel machine with built-in speaker, remove the tape apparatus and leave the amp, make a new faceplate and build the Korg into it. Along with your theramin, exponential converter, and whatever other modules of yours I can fit of course. Maybe a couple of ribbon or other small touch controllers...
It will be like the spawn of an EMS Synthi A and an Ondes Martenot that mutated and sprouted antennas.

No, no, no!

Don't strip out your reel to reel - convert it to a tape delay and work around the components to make the world's only Ondes Theresynthi with on-board echo!

That's exactly what I was thinking, but the thing is packed so full with motors, belts, transformers, and gears that its probably way beyond the capacity of the case and my abilities to rearrange to do that.
But that can't stop me from getting a little portable dictaphone reel machine that takes 3" reels and a couple extra heads to make a little phrase looper and echo module that fits on the face!