There's a great 80-minute documentary about Theremin – I heartily recommend it. The highlight is a very trippy interview with Brian Wilson of the Beach Boys -- the interview really has to be seen to be believed:

https://www.youtube.com/watch?v=j_0WmqnC6eA

Looks like the documentary is no longer on Netflix, but it is on Amazon Prime streaming. Rotten Tomatoes for the movie:

https://www.rottentomatoes.com/m/theremin_an_electronic_odys...

And if you are interested in buying a Theremin:

https://www.moogmusic.com/synthesizers?type=52

Interesting? Wikipedia article doesn't even get close. There are various accounts of his life and achievements, memoirs of witnesses, people who knew him in various contexts, the descendants/family, records of his own recollections -- all available on Internet. Unfortunately, most of it is in Russian. Reading it gives you that messy, undefinable feeling of experiencing a genius.

There are a surprising number of popular songs which have actually used the theremin. Perhaps the most recognizable is "Good Vibrations" by the Beach Boys. You can hear the theremin especially clearly in the background of the first chorus.

https://www.youtube.com/watch?v=Eab_beh07HU

Theremin playing a theremin https://www.youtube.com/watch?v=w5qf9O6c20o