When a flying saucer circled over Washington, DC, in the classic 1951 sci-fi film, “The Day the Earth Stood Still,” it did so to music played on an electronic instrument known as the Theremin.

Its Russian inventor, Leon Theremin, was born in St. Petersburg on today’s date in 1896. In 1927 Theremin traveled to America, where he obtained a patent for an electronic instrument he called the Thereminovox. In the 1930s, Theremin arranged concerts for his creation at New York’s Carnegie Hall.

Then, in 1938, without explanation, Theremin disappeared. Some said it was because he was in debt, others because he was married to two women at the same time. The truth was even stranger: Theremin was a spy.

He had been passing on American technical information to the Soviets. Ironically, when he returned home, Theremin was immediately thrown into a Soviet prison for seven years. While incarcerated, he developed miniature electronic eavesdropping devices for the Soviet government.

Decades later, in 1989, as the Soviet Union was collapsing, the 92-year old Theremin again showed up in New York to be honored at a festival of electronic music, amazed that his name and instrument were even remembered.