Depends on which theremin, in which hands, with which effects, or lack thereof.
Does this sound unpleasant to you? https://m.youtube.com/watch?v=62lT9XsZVio (maybe it's subjective, but it sounds very pleasant to me).
Does this sound unpleasant to you? https://m.youtube.com/watch?v=62lT9XsZVio (maybe it's subjective, but it sounds very pleasant to me).
The comment in the other reply to the parent comment, as well as what I've heard of Carolina Eyck's playing, do sound pleasant to me though.