"Did I miss a part of the conversation?" - M Wessel
Yes, Yngvox Moogsteen deleted his post for some reason. Which is why I always make it a point here to embed the thing I'm responding to.
"Is it possible to get a D-Lev theremin?"
I'd love to be able to help you, but I can't at the moment unfortunately. Supply chains to the US are currently a mess, and the FPGA board has become quite scarce and expensive (aging out? bitcoin miners? grrr...) so there's a waiting list. I'm trying to scrape together enough parts to make another measly 14 or so but Amazon and eBay have inexplicably sent a couple of my packages to Texas and Virginia (and don't get me started on FedEx!).
Pitch is the main problem with unattended use, it might be possible to modify the Etherwave with a small processor that looks at the pitch difference and constantly but very slowly nulls it (the oscillator null is actually a voltage control point, which would facilitate this). The D-Lev can optionally do this, and the null rate is actually bi-modal to quickly adapt to an empty room. It also nulls the volume for closer = louder to totally shut the thing up when no one is around.
Another possibility is putting an OpenTheremin in there, with a special software load. I know of two Theremin World members who have worked on the OpenTheremin code, Thierry and Mr_Dham (Vincent), but I don't know if they can assist you in this regard or not. The code is open, so you might be able to get someone else to help you modify it, and I think this is perhaps your best, easiest, and fastest solution.
What you really need (and what all Thereminists really need) is something like the OpenTheremin but with higher voltage fields and more processing power. Vadim (Buggins) has been working on that here: http://www.thereminworld.com/forums/T/32640?post=215938#215938