What's a theremin?

Back in the early 1900's, a Russian physicist named Leon Theremin invented a musical instrument based on proximity sensors. In layman's terms, this means that the instrument is played without any physical contact. The performer on a theremin moves her hands between two metal antennas, which pick up the movement and turn it into sound waves. This is what it looks like:

I came across this instrument fairly randomly, and discovered a performance by Carolina Eyck, who specializes in the theremin. The first time I saw it, and didn't know what the instrument was, I started looking for the strings. But there weren't any! 

Here is her rendition of the Queen of the Night aria from Mozart's Magic Flute. A very different kind of music, but quite pleasant to hear.

Happy Monday.