On the Tech & DIY > Schematics page you will now find the complete 18 page RCA Theremin Service Notes from November 1929 with schematics, circuit descriptions and lots of debugging information.
You will also discover that a new category has been added to the Tech & DIY section: "Other historical electronic instruments". I started uploading two Trautonium related files, a method from 1933 written by the Trautonium's inventor Dr. ing. Friedrich Trautwein and an article from a electronics magazine which was published by Trautonium virtuoso Oscar Sala in 1943. The latter discusses many sound generation, wave shaping and linearity issues. This might also be of interest for many Theremin builders. Enjoy!
The Trautonium documents are in German and I have unfortunately neither the time nor the rich English vocabulary which is needed to translate them. But I'm ready to answer specific questions.