My name is Randy George and I am a thereminist. Thanks for checking out my channel.
The theremin is the only musical instrument that converts motion into a continuous stream of sound... without physical contact! Every little motion in the space around the instrument affects its sound. To place notes correctly the player must be sensitive to intonation and develop precise control over the hands and arms to convert patterns of coordinated motion into music.
The theremin has the reputation of being the most difficult instrument to master (as a melodic instrument) because of the combined challenge of managing its unusual playing interface and the zen-like body stillness required to stay on pitch, on key, in tune.
It can be used carelessly as a toy or played very carefully as a fine expressive musical instrument. It depends entirely on the player.