[gibspaulding]

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

[alexhornbake]

Common mistake. Good vibrations did not actually use a theremin. It was a ribbon controller type instrument that was designed to mimic the sound. Theremins are hard. https://en.m.wikipedia.org/wiki/Electro-Theremin

[Stratoscope]

Somewhat fittingly, the Electro-Theremin is seen being played at 4:20 in the Brian Wilson interview that gibspaulding posted:

https://youtu.be/j_0WmqnC6eA?t=257

[Nition]

In terms of actual Theremin music, here's Clara Rockmore's Nocturne In C# Minor [1975]: https://www.youtube.com/watch?v=ghWdgcYIcSk