In the mid 1930's, Leon Theremin built three custom instruments that we know of: two for his patroness Lucie Bigelow Rosen, and another similar one for Clara Rockmore. These instruments were more elaborate than the RCA theremins and had, among other things, ten different timbre settings. Thereminist Howard Mossman, who has been a tireless supporter and promoter of the theremin for longer than most of us have been alive, has generously opened his personal archive and allowed me to use these rare photos of the inside of Clara Rockmore's instrument. These unique photos were taken with Mrs. Rockmore's permission in the 1990's by thereminist and vintage theremin expert, Reid Welch, a personal friend and confidant of the late Mrs. Rockmore. Experts who have examined the circuitry of this theremin agree that it has all the elegance and simplicity of design that one would expect from a genius like Leon Theremin.
Both Clara's instrument and the one built for Lucie Rosen were equipped with a small light that would glow whenever the thereminist played an A. In this way, the theremin could give a band or orchestra an accurate note from which to tune. You will notice there is a door in the front of this instrument (with what appears to be a string attached to the small knob that opens it). This is for access to the front compartment where the tubes and other vital components are housed. The rear compartment was reserved primarily for the coils.
THE REAR COMPARTMENT
It is my understanding, based on comments made regarding Clara's theremin by the late Robert Moog, that the wheel that can be seen on the outside of the cabinet just below the volume antenna was the timbre control. Clara Rockmore had one particular setting that she preferred and did not use the others.
Unlike the RCA theremins, these custom instruments had a separate front access compartment for the radion tubes. There is a wooden panel separating the front and rear compartments and many of the coils, condensers and other parts have been meticulously fixed with small brass screws to this panel.
THE FRONT COMPARTMENT
These last three photos are details of the front compartment where the tubes were housed. There is a power transformer bolted to the floor of the left hand side (volume antenna side) of this compartment, and the tube sockets are in the vertical panel (or back wall) which separates the front and rear of the instrument. In the lower right corner of the photo above you can see the UY 224 radion tube with its distinctive cap clip.
The photo above is a detail of the right hand side of the front compartment (the pitch antenna side) showing two clearly visible modern D batteries. It is probable that these batteries, along with other obviously recent parts and wires, were added by Robert Moog during the course of his restoration and maintenance of this instrument in the early 1970's.