The most important thing about a theremin technique, whatever it may be, is that the person using it be satisfied with it. There is no "right way" or "wrong way" to play the instrument, and you're not competing with anyone but yourself.
From the point of view of control, however, there are more efficient and less efficient ways to play. The more control you have, and the more you use it to add variety and passion to your playing, the more interesting your music will be. We have very few resources when it come to the theremin, so we need to use everything that is available to us. Unlike players of traditional instruments who can change the timbre of their sound through bowing technique, breath control, finger placement, etc., thereminists are stuck with a tone that cannot change color. Once we have chosen our timbre settings, we're stuck with them for the duration of the piece we are playing. We have only volume and pitch with which to communicate whatever it is we have to say musically. How we use these two resources will be determined by our own sense of phrasing, vibrato, expression, etc.
One way to increase control and precision in theremin playing, is to spread the tasks of intonation and vibrato (the two jobs of the pitch arm/hand) among as many muscle groups as possible. This will give the player greater stamina and allow for more subtle shading of the sound. Essentially we have biceps, triceps and finger extension to work with. Clara Rockmore played vibrato using a back and forth motion of the forearm while intonation was done with extensions of the fingers. Dalit Warshaw takes the opposite approach. She plays vibrato with extensions of the fingers (called the "finger wiggle") and accomplishes intonation with the forearm. She frequently adds definition to her intonation with a technique I have not seen anywhere else, a "rabbit ear" popping up & snapping shut of her index and middle fingers. I would be extremely surprised if this was a method that Clara Rockmore taught her!
The question here is: Is this the best way to play the theremin for maximum control? I would say probably not. The more difficult the melody is that you are trying to play, the greater will be the disadvantage imposed by this technique. This is the problem with all the various methods that people have arrived at by default. They seem to work beautifully for the beginner playing fairly simple pieces. It's not until you attack much more difficult compositions that you hit the invisible wall. I have often compared this to a two-fingered typist who uses only the index of each hand. It works. And some people use it with surprising speed - but they're never going to win the typing contest!
I just listened to my own recording of the Faure PIE JESU with the intention of posting it for comparison. I recorded it about ten years ago around the same time as I did the Julian Lloyd Webber PIE JESU. Unfortunately it's a piece of shit. What the hell was I thinking?!
