basic experiments

Thank you Valery for your frank words. I think similar as a musician and look for the basics as a physicist. 

The missed short attack effects have been overcome since the genuine solution of Dominik Bednarz for the volume control. Wished you could try it. 

And: yes, it is a necessary add and the best new thing after many, many years of stagnation in theremin progressing! My volume attack response also can react very fast, without a change in any knobs. Only the hand movement acceleration decide between a slowly crescendo or a fast plug.

Maybe the new Claravox adsr function goes in that direction, but I suppose, Moog comes from the classical synthesizer world and so you have to change the response behavior and it is not the naturally hand movement, that the volume follows as you want express the loudness.   

I hope no one thinks I'm being overly critical of these interesting coupling experiments, this is research that absolutely should be done and I applaud it.  But one thing that coupling gives (e.g. the RCA) is a distinctly different waveform to the low end.  A positive side effect of this is to break up the "meowing" or pitch-based vowel sound that, once you become aware of it, you can't unhear it.  Resonances are largely fixed in natural sounds, and fixed waveforms usually give a "tracking filter" type timbre which is quite unusual sounding (outside of the synth world).  IOW, capturing/replicating timbre via waveform methods needs some method to significantly alter the waveform based on pitch in order to avoid unnatural sounding timbre transitions throughout the pitch range.

Ah yeah, Dewster, "meowing" that does describe what I noticed trying an EW that had been fitted with an ESP01 module and which I didn't like about it. An adjustable or at least trimmable amount of coupling would be a good thing I imagine.
An option that the Theremini's synth gives is modulating the timbre with the volume loop side, and I find that using an envelope filter effect can do the same, so for example from low volume to loud the formant changes from U/O in the direction of Ah. Many natural instruments also tend to get brighter with a louder volume and I find using the effect subtely (depth setting near or at it's lowest) sounds good and quite natural to my ears.
JPascal, did you basically use a YAEBM circuit with a small capacitor or a resistor to couple the oscillators to some extent, or something else of your own design?

An option that the Theremini's synth gives is modulating the timbre with the volume loop side, and I find that using an envelope filter effect can do the same, so for example from low volume to loud the formant changes from U/O in the direction of Ah. Many natural instruments also tend to get brighter with a louder volume and I find using the effect subtely (depth setting near or at it's lowest) sounds good and quite natural to my ears. - DreadVox

This is getting somewhat off-topic to the thread, but as an early-adopter of Dewster's D-Lev digital theremin I want to respond to this so that he doesn't need to.  His design has many user-settable modifiers that allow pitch and volume to influence various parameters of the internal synthesizer.  If you look at a typical voice preset screen shot from his librarian, any time you see "pmod" or "vmod" this represents a pitch or volume modifier that is applied to the parameter in that particular box.  You can use these to modify everything from pitch-preview volume to formant frequencies.  He has spent a good amount of time studying how instrument and vocal timbres vary with pitch and volume, and he has this covered pretty well, I think.

The digital theremin offers a lot of new pathes. That is surely a fact, pitts8rh. (I think Dewster is well noted in TW). The musicians always have to decide, what from the manifold options are the best for their interpretations, genres and so on.

Now some useful and helpful things concerning the buffering or reducing coupling effects between the pitch oscillators. As is so often the case, there are already good and published things here.

The best idea I found is a brigde which compensates the direct coupling theoretical completely.

German engineer A. Klaus used a bridge for the Etherwave with a R-C-connection between the hot sides of the two 15 pF coupling condensors.  R=150 kOhm, C=1...5 pF. The C can simply made with a short piece of twisted isolated wire. A very good description and a video please find under his website here, I highly recommend it:
http://aetherwellen-musik.de/Theremin-Instrumente/Instruments/EW-Standard-Theremin-Modifications

I made a reduction, not compensation by a C bridge over the 10 kOhm resistor to the 4,7 kOhm/4,7 nF RC demodulator-combination. To find a proper value a variable air condensor can be used. I found 56 pF for me a good compromise.

Of course there are the proper buffer solutions by Thierry, Dewster, Dominik,Valery. And if you want a more sine wave envelope at the rectifier diode you can use different and not equal coupling condensors of 15 pF, for example 5 pF and 20 pF.

Here is the most minimal invasive solution I made. And now I will deal with my stuff, not in more or less enhancements for the most commercial and popular theremin Etherwave.

   

"A very good description and a video please find under his website here, I highly recommend it:

http://aetherwellen-musik.de/Theremin-Instrumente/Instruments/EW-Standard-Theremin-Modifications" -JPascal

Thanks for posting this link.  It is a very good article, and one that has never shown up in my Google searches.

JPascal, thanks for routing to A. Klaus. Hats off! Like Roger i have missed that article.
And your single-component bass extension: nice!

http://aetherwellen-musik.de/Theremin-Instrumente/Instruments/EW-Standard-Theremin-Modifications

Yes, nice article, thanks for the link!  (I am so happy that I'm not in the analog Theremin business.)

(I am so happy that I'm not in the analog Theremin business.)

I am so happy that i am in the analog business.