Theremin out of large steel tube.. possible?

"dewster, would your approach be swamped with 50/60 hertz hum from the environment? The amplitude of the AC field would be fairly constant so touching the wall of the cylinder could shift the level to trigger a midi single note sequence per touch?"  - Christopher

Good point, this would probably be better done via offset heterodyning and digital means, where notch filtering could be used to squash the mains field.  Note triggering could be via large capacitance shift.

"Who is going to make all this stuff, is it practical?"

Who knows ;-)  I'm just tossing my 2 cents in.

"Amazon has this"

I don't think that thing would tolerate a 100V sinewave at its input very well (nor would a Theremin oscillator likely tolerate it).

dewster and christopher - you guys are absolute legends. I am putting my proposal in for this whole this in the coming few weeks and will start fabrication in about a month or so. I'll keep you posted. I love the idea of amplifying something like a heart beat in there - had crossed my mind too. Would be an awesome experience... Thanks so much for the model dewster! Once I have had a chance to properly absorb all this through some local help I'll let you know what happens / problems / etc.

THANK YOU!