Basic Ondes Martenot plans

Greetings,
Does anyone know of, or can point me in the direction of any site or thread that has some sort of basic/advanced plans to how an Ondes Martenot works? Or construction of?

Theremin construction guides are everywhere, I still have yet to see any guides that can even tell you how to make the most basic version of the Ondes Martenot.

The Ondes is still under patent, I believe. I don't think it has ever been a hobbyist-constructed instrument.

I am in the midst of restoring an Ondes Martenot 6 now. The instrument is basically hand made. I had to draw my own schematics. This is not something that even a sensible pro would tackle. The electronics are pretty straightforward but the mechanical aspects are challenging. I have built two theremins, one a RCA copy and have restored a RCA Theremin to new condition and that is where I would start.