> Someone did do a PIC-Theremin project in EPE magazine a couple of
years
> ago, but it had a potentiometer as the
> volume control, and I thought that was a copout (wasn't even a sliding
> pot, as I remember!).

The volume side is the least understood by most people.
A fixed oscillator is run through a filter circuit, which the "antenna"
is part of. Your hand capacitance varies the center of that passband.
The RF that passes through the filter is detected, and the level then
sets the volume through a VCA. 

The pitch side though, is where the "magic" happens.  There is a tuned
circuit on the "antenna" which is hard to explain in simple terms. It's
SRF is VERY close to the operating frequency, which amplifies and
linearizes the pitch scale, but only if properly tuned.  It's far more
complicated than just a body capacitance tuned VCO.

> The famous Beach Boys' use of a Theremin in "Good Vibrations" is dodgy
too
> - seeing the film of them doing it,
> the pitch control is done using a sliding shorting bar on a pair of
rails,
> which makes it just a VFO in my
> opinion, not a real Theremin.

It's a theremin variant. 



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