Issue 155 June 2003
Good Vibrations

---

---

Start • Down to Earth • SI(G)NS • Hands On • Bags and Beyond • Sources and PDF

Have you heard the story of Leon Theremin and the musical instrument named after him that he invented almost a century ago? Actually, to be correct, the story is really about Lev Sergeyevich Termen and his cathode electromusical instrument. (The Russian-born inventor changed his name when he moved to the United States in the early ’20s.) Anyway, it’s an eminently interesting tale, and the subject of plenty of ’Net hits (start at www.thereminworld.com or just search for “Theremin” on Google) and even recent books and movies (see Photo 1).

(Click here to enlarge)

Photo 1—Theremin, who is now the subject of books and movies, exploited the concept of hand capacitance almost 100 years ago. Source: A. Glinsky and R. Moog, Theremin: Ether Music and Espionage (Music in American Life), The University of Illinois Press, Champaign, IL, 2000.

The story goes well beyond technology and music, combining depression-era Americana and Cold War intrigue. To this day, there are still questions about the circumstances of his “kidnapping” (or voluntary return?) in 1938. Back in the Soviet Union, Theremin was forced (or chose?) to develop spy gadgets for the KGB. One of his first inventions was the bug planted in a gilded eagle given to the U.S. Ambassador by Soviet “Boy Scouts” in 1945. Meanwhile, on the home front, RCA made about 500 theremins in the ’20s, and those that remain are collector’s items today.

Well, maybe you haven’t heard the Theremin story, but it’s almost inconceivable you’ve never heard the ethereal tones produced by one of the first purely electronic musical instruments, seminal ancestor to the synthesizers and MIDI technology you’ll find in today’s music studios. Indeed, the well-known synthesizer pioneer Robert Moog got his start by home brewing theremins, and he’s still working with them to this day. (You can find his how-to articles on the ’Net.) [1, 2]

The theremin came into its own in the ’50s, providing the audio signature for various invaders from outer space, which is all the more ironic given the Cold War backdrop to the age. I’ve got to laugh at the fact an instrument designed by a KGB guy ended up being a musical calling card for faceless Sputnik-on-steroids evildoers such as robot Gort in The Day the Earth Stood Still (1951) and the furious queen in Queen of Outer Space (1958).

Subsequently, theremins enjoyed some niche success on the musical front in the ’60s and ’70s. Although bands like Lothar and the Hand People had arguably limited reach, there are better-known theremin players up to and including Led Zeppelin’s Jimmy Page.

The famous “wee-ooh” sound of the Beach Boys’s 1966 hit “Good Vibrations” was perhaps the celebrity highpoint for the theremin, at least in spirit if not fact. Actually, the Beach Boys used a so-called electro-theremin, which was an instrument built in the ’50s that used a mechanical pitch slider controlling a sine wave oscillator.

I CAPACITOR

Putting the Beach Boys and B-movies aside, Theremin’s invention still resonates today with practical application. The theory of operation represented at the time a breakthrough for the heterodyne concept. You may recall the idea: mixing two sine waves of different frequency will produce a beat frequency equal to the difference between the two.

Of course, the most striking feature of the theremin was its seemingly paranormal operation, in which a player would wave their hands in proximity to two antennas, one for pitch and one for volume. A newspaper article at the time reassured readers that it was all based in science and explained that they needn’t worry that the instrument was monitoring their thought waves.

The key to the whole scheme is the fact that humans are capacitors, albeit small ones. Who hasn’t had the experience of affecting a piece of electronic gear’s operation by proximity, whether fuzzy TV reception or a balky chip?

Theremin exploited so-called hand capacitance to induce a relatively small change in a tuning oscillator relative to a fixed (a.k.a. “local”) oscillator. Thanks to the heterodyne principle, even a relatively minor difference between high-frequency oscillators can sweep the audio range (e.g., a 1- to 1.02-MHz difference covers 0 to 20 kHz).