I am disabeled, and need some help to play the Etherwave Plus. Would the Yamaha FC7 Volume Pedal work connected to the Volume CV Output to control the volume?
Ed
No, that is an output jack that sends control voltages. I don’t believe your pedal will work at all with your theremin as you expect.
You’ll need something like a Morley volume pedal plugged into the audio output of your theremin, with the other end of the pedal plugged into an amp or a mixer. Unfortunately, this will not allow you to hear your volume changes using the headphone jack on the theremin. However, many mixers have headphone jacks.
The Morley “Optical Volume” (Model EOV) might be a good pedal for you. It uses an optical resistor instead of a potentiometer (won’t wear out and get scratchy), uses an audio taper so it will act as a true swell pedal, and is made to work with keyboards, so you should get the full tonal range of your theremin. They go for around $70.
Good luck!
Bob
Thanks Bob, you saved me $50. I lack mobility on the right side, I have to use my left side which is normal. So I can play it on the floor with my left foot on V and my right hand on T. Except the ceramic tile floor reacts with the V and turns it off. So I lifted it 5" by putting it on a violin case, disconnected the V on the non energized connector, turned it straight up, and roll my left heel on a 2" box when activating the V.
I also play the violin. I can bow with my right hand moving across my body, the violin is on my left, upright and facing the same direction as me. I use a Row-Right, and a strap around my neck to keep my arm from dragging.
I also ride a tricycle with that horn looking thing on the right so I can grip it, and a left pedal with teeth so my foot doesn’t slip off.
I would be glad to entertain questions about disabilities from anyone. Ed
After hearing what you go through just to play your instruments, I am absolutely struck with how much I take for granted! 
Using your foot to manipulate the volume antenna is a brilliant idea! And it sounds like the pitch antenna is unaffected by the violin case. Very cool! 
I’m very glad I was able to be of service. Please keep us all posted on your progress.
Bob
The violin case is really a gig bag, rag & foam. Ed
Any old port in a storm, eh? 
This is off topic but you would be suprised how much we take for granted if we should lose a limb or the usage of half of our body. EVERYTHING is different. Just to get an idea, try to button your shirt with one hand or buckle your belt.
But what is remarkable are people who despite their disibillities, try to persue their interests. To me it is a tragedy when something happens to someone that would not let them create or would negate what they were naturally born to do.
Back to topic,
I have used the Morley Wah’s before and they feel really good and sound good. Their volume pedal should be high quality.
I considered getting a volume pedal for my theremin, some say that it is cheating, but I want to be able to play synths and accent notes within the zero beat, and I would need a volume pedal to control when youd hear the theremin. I like using the theremin as an accompanyment rather than traditionally. It just depends on what wets my whistle at the time.
Eric
The toughest steak I’ve ever had, was no steak at all! (My Dad was always fond of saying that.)
I recently learned that Leon Theremin had theremins that used a pedal to control the volume. (Edit: In fact it was for his first instrument, the Etherphone, that he used the volume pedal.)
Thanks for the bump on the Morely, I’ve always liked the idea of their optical pots.