Control theremin pitch with cv from eurorack

Hello dear theremin lovers. 

I am posting to ask a question that might be a bit upsetting to a theremin lover 😅. 
Before a couple of years, my girlfriend had a short lived infatuation with theremins and bought a tube theremin from Pegna. It's been sitting in a shelf completely unused since then, and I've been thinking I could maybe somehow control the pitch of its wonderfully sounding tube oscillator with my modular. Now I know this pretty much dethereminizes a theremin, but it's still better than leaving it completely unused. 

Does anybody know how I could go about it and if it's a possible mod for someone with a very basic knowledge of electronics? There's a visible bare wire that leads to the pitch antenna (!) . Would it maybe be enough if I connect that wire and another one for ground (assuming I can find the ground inside the theremin) to a jack socket and then just plug a eurorack cable ?

Thank you all in advance

Hello Christopher and thank you for your answer. 
I didn't buy a theremin in order to modify it and control it with eurorack, that would not make much sense indeed. I happen to already have one lying around, bought by my gf, and since I don't wish to use it as a theremin, I am trying to see if I can put it's wonderfully sounding oscillator to good use. Selling it is not a possibility, as it's not exactly mine. 

My hope regarding this mod was that it's not like trying to turn a guitar into a banjo. It's an oscillator whose pitch is controlled by an antenna and I would like to also be able to control it with cv from my modular. If that's not the case and it's much harder to do, I would appreciate an explanation :-) 

I’d love that Theremin.  Just trade me for a guitar, sitar, accordion or other instrument, if interested.  Sounds great and would be a privilege to own.  Don’t alter it.
Thanks 

Your girlfriend just needs a new toy.

Ps.   Even a banjo if your girlfriend is interested.  I have many instruments, mostly stringed but have come to love the Theremin.  Getting Rid of a few instruments but always looking for a new great sounding Theremin.  Yours sounds exceptional.  
Also tube amps for trade.

PSps.  Also have a Banjo-guitar...

"There's a visible bare wire that leads to the pitch antenna (!) . Would it maybe be enough if I connect that wire and another one for ground (assuming I can find the ground inside the theremin) to a jack socket and then just plug a eurorack cable ?"  - yoreb

No, it's not nearly that easy, unfortunately.  The wire senses minute capacitance changes in a non-linear way, so it would require something like a varactor diode, a bias source, and some software to linearize things.

From the video it looks like a nice Theremin, why don't you learn to play it?

Hello Dewster and thank you very much for your answer. You mean that the diode, the bias source and the software are all needed just to deal with the non linear response and for the rest the connection I described will work? 

If that's the case, that should not be a big problem, as there are already modules within eurorack to deal with that. I even don't mind the non linearity as I don't plan to control it with a keyboard.
Do you have any idea what voltage range would be safe regarding the cv I send? 

By the way I have already learned how to play it as a theremin a bit, and if I ever go forward with the mod, I would like to do it in a way that doesn't kill the antenna

"You mean that the diode, the bias source and the software are all needed just to deal with the non linear response and for the rest the connection I described will work?" - yoreb

No, Theremin antennas are sensitive to small capacitance changes, and a varactor diode acts as a variable capacitor (the band gap capacitance varies with applied voltage).

It should be not impossible to implement your pitch control idea with an simple external varactor diode circuit to "mimic" the hand capacitance. This makes me a bit curious to do some basic experiments...

Are there any details of that nice Pegna theremin model in the universe?

It should be not impossible to implement your pitch control idea with an simple external varactor diode circuit to "mimic" the hand capacitance. This makes me a bit curious to do some basic experiments...Are there any details of that nice Pegna theremin model in the universe?

 Unfortunately I dont think you can find schematics of the Pegna Theremin.. I also haven't been able to contact the guy up to now, might try again. 
But please let me know if you have any specific idea of how I could do it! 

Do you have an oscilloscope? Which frequency is measured when you approach the pitch antenna with the bare probe? Which DC voltage range does the Eurorack-CV-out sweep exactly opposite ground?