Radio experts can tell you that Professor Theremin has taken the familiar howl of an unbalanced receiving set and persuaded it to play Schubert's "Ave Maria." The result, which seems to us more important than the mechanics involved in obtaining it, is a tone which varies from something like cello timbre to the vibrations of the musical saw.Romantic, yes. Clara Rockmore did her best to lend credibility to the instrument but it never joined the clarinet in regular orchestras. Theremins did show up in sci-fi film scores, and later in scattered pop songs...though much music retroactively credited to the Theremin was actually performed on the Ondes-Martenot, much to my personal disillusion.
The Theremophone is still in a transitory stage, we hear, and it has obvious disadvantages. As the flow of tone is continuous, it is impossible to avoid at least a suggestion of scooping, and there are not yet Teremophonists sufficiently skilled to play rapid or complicated passages... Nevertheless, here is a new musical instrument, which is based on the fundamental principle underlying all instruments and which may, in less time than one might fancy, become part of the orchestra. If this seems romantic, so once upon a time was the notion that the clarinet belonged in good symphonic society.
I have seen Theremin and Theremin-ish instruments played; they keep on popping up at Legendary Pink Dots shows in one form or another. It's beautiful to hear and even more beautiful to watch, but does seem to lack diversity and still can't be played at any speed or accuracy (unless, again, you're Clara Rockmore).