Theremin’s accidental discovery was that the electromagnetic field around an antenna could be affected by merely moving your body into that field. “It’s simply the electromagnetic fields in your own body, what we refer to as capacitance, affecting the circuitry through the electromagnetic field surrounding some device,” says Albert Glinsky, an American composer and the author of Theremin: Ether Music and Espionage. After Theremin’s initial discovery of the sonic potential of his former gas meter, he altered the device into a working instrument. He placed one antenna vertically and one horizontally, meaning that a player could control pitch with their right hand and volume with their left, producing real melodies out of thin air.

As word of Theremin’s new invention spread, he was invited to an audience with Vladimir Lenin, at the time the Chairman of Russia’s new Bolshevik government. Lenin absolutely loved the new instrument. “He was so taken with it,” Glinsky says, “that in 1922 he sent Theremin all around the Soviet Union to demonstrate the instrument as propaganda for electrification.” The idea was that villagers would be so impressed by Theremin’s instrument they’d be motivated to bring the magic of electricity into their homes. Already, Theremin’s invention was serving a dual purpose – to entertain and to support his nation’s interests – an intertwining of intentions that would continue for almost his entire life.

After his successful tour of Russia, in the late 1920s Lenin sent Theremin to Western Europe, where the legend of his mysterious instrument quickly grew. “Theremin gathered huge crowds, because it was such a fascinating thing to see this man stand in front of what looked like a little wood writing desk with two metal antennas, and with nothing but his hands in mid-air, produce these melodies, sounding like a soprano singing,” Glinsky explains. “It was considered magic at the time.”

What audiences didn’t know was that Theremin was already working as a spy for the Soviet regime. While he wowed crowds with his ghostly tunes, played on what was then called the Thereminvox, or “Theremin’s voice,” he kept his eye out for any information that might be useful to report back to his homeland. “This was the great ruse, because everybody was so focused on this magician pulling music out of thin air that he was able to gain access to industrial places and patent offices and all sorts of things,” explains Glinsky.

In 1927, Theremin made his way to New York City, where he patented his instrument and made a deal with RCA for the rights to produce 500 of what they now called simply “the theremin.” “RCA marketed it as the instrument that anyone could play,” says Trevor Pinch, author of the history of synthesizer music Analog Days. “This was a huge mistake.” It turned out that playing the theremin was anything but easy. With no keys or fretboard to hold onto and no visual reference points, it took years of practice to play the instrument with any competency. “It would almost be like if you had a piano where the size of keys changed each time you sat down to play it, so you weren’t sure how far apart your fingers had to be to play a scale,” Glinsky says. Unsurprisingly, RCA’s gamble didn’t pay off. Though they sold most of the instruments they built, the theremin wasn’t anything like the hit they’d hoped it would be.

While living in America, the gap between Theremin’s two lives grew more dramatic. While he cavorted in New York with the likes of Albert Einstein, taught the theremin virtuoso Clara Rockmore and entered into a controversial marriage with the African-American prima ballerina Lavinia Williams, his espionage mission continued. This double life wouldn’t last long. The lead-up to World War II made Theremin increasingly nervous that his activities would be discovered, and in September of 1938 he fled the USA without even informing his wife of his planned departure. Thus began a long period during which Theremin’s whereabouts were totally unknown to people in the West, leading to suspicions that he’d been kidnapped by Soviet agents. Glinsky thinks those theories are ridiculous: “He was simply not kidnapped; it was not that mysterious,” he says. “The FBI had a file on him, he had lots of debts and was running out of steam in many ways.” These problems are what really forced him to flee, but it turned out to be a more permanent disappearance than anyone could have predicted: Theremin wouldn’t return to America until 1991.