Conversation so far:
What is a theremin?
Upon release, the single Good Vibrations prompted an unexpected revival in theremins and increased the awareness of analog synthesizers.
What single by the Beach Boys prompted an unexpected revival in theremins and increased the awareness of analog synthesizers?
Although the song does not technically contain a theremin, Good Vibrations is the most frequently cited example of the instrument's use in pop music.

Question: What did they use it for?
Self-contained rewrite: What did the band the Beach Boys use the theremin for?