The sound of the theremin has become synonymous with the spectral and spooky sci-fi horror flicks of the 1940's and '50's. It's trilling oscillations conjure up images of flying saucers made from hub caps and fishing line. When most folks hear and see the theremin they tend to think of it as little more than a novelty or scientific amusement. While it may have fallen out favor in horror movie soundtracks it has remained a mainstay within the field of electronic music. It is distinguished among all musical instruments by being the only one that is played without touching the instrument itself. To the radio and electronics buff the theremin is worth exploring as a way of learning about electromagnetic fields and the creative use of the heterodyning effect for artistic purposes. Whether or not the quivering sounds the instrument pulls out of the ether are appealing to a listener is a matter of individual preference.
The inventor of the theremin, or etherphone as it was first dubbed, was Lev Teremen. He was born in Russia in 1896 a few years before Marconi achieved wireless telegraphy. As a young boy he spent his time reading the family encyclopedia and was fascinated by physics and electricity. At five he had started playing piano, and by nine had taken up the cello, an instrument that has an important influence on the way theremins are played. After showing promise in class he was asked to do independent research with electricity at the school physics lab. There he began an earnest study of high-frequency currents and magnetic fields, alongside optics and astronomy. It was around this time Lev met Abram Ioffe, a rising physicist whom he would work under in a variety of capacities. Yet his studies in atomic theory and music were overshadowed by the outbreak of WWI. In 1916 he was summoned by the draft and moved to Petrograd where his electrical experience saved him from the front lines. He was placed in a military engineering school where he landed in the Radio Technical Department to do work on transmitters and oversee the construction of a powerful and strategic radio station. In the course of the war the station had to be disassembled and Lev oversaw the blowing up of a 120 meter antenna mast. Another war time duty was as a teacher instructing other students to become radio specialists.
As Lev's reputation grew among engineers and academic scientists he was eventually asked to go and work with Ioffe Abram at the Physico-Technical Institute where he became the supervisor of a high-frequency oscillations laboratory. Lev's first assignment was to study the crystal structure of various objects using X-Rays. At this time he was also experimenting with hypnosis and Ioffe suggested he take his findings on trance-induced subjects to psychologist Ivan Pavlov. Though Lev resented radio work in preference for his love of exploration of atomic structures, Ioffe pushed him to work more systematically with radio technology. Now in the early 1920's Lev busied himself thinking of novel uses for the audion tube.
His first project involved the exploration of the human body's natural electrical capacitance to set up a simple burglar alarm circuit that he called the "radio watchman". The device was made by using an audion as a transmitter at a specific high frequency directed to an antenna. This antenna only radiated a small field of about sixteen feet. The circuits were calibrated so that when a person walked into the radiation pattern it would change the capacitance, cause a contact switch to close, and set off an audible signal. He was next asked to create a tool for measuring the dielectric constant of gases in a variety of conditions. For this he made a circuit and placed a gas between two plates of a capacitor. Changes in temperature were measured by a needle on a meter. This device was so sensitive it could be set off by the slightest movement of the hand. This device was refined by adding an audion oscillator and tuned circuit. The harmonics generated by the oscillator were filtered out to leave a single frequency that could be listened to on headphones.
As Lev played with this tool he noticed again how the presence of his movements near the circuitry were registered as variations in the density of the gas, and now measured by a change in the pitch. Closer to the capacitor the pitch became higher, while further away it became lower. Shaking his hand created vibrato. His musical self, long dormant under the influence of communism, came alive and he started to use this instrument to tease out the fragments he loved from his classical repertoire. Word quickly traveled around the institute that Theremin was playing music on a voltmeter. Ioffe encouraged Lev to refine what he had discovered -the capacitance of the body interacting with a circuit to change its frequency- into an instrument. To increase the range and have greater control of the pitch he employed the heterodyning principle. He used two high-frequency oscillators to generate the same note in the range of 300 khz :-beyond human hearing. One frequency was fixed, the other variable and could move out of sync with the first. He attached the variable circuit to a vertical antenna on the right hand side of the instrument. This served as one plate of the capacitor while the human hand formed another. The capacitance rose or fell depending on where the hand was in relation to the antenna. The two frequencies were then mixed into a beat frequency within audible range. To play a song the hand is moved at various distances from the antenna creating a series beat frequency notes.
To refine his etherphone further he designed a horizontal loop antenna that came out of the box at a right angle. Connected to carefully adjusted amplifier tubes and circuits this antenna was used by the other hand to control volume. The new born instrument had a range of four octaves and was played in a similar manner to the cello, as far as the motions of the two hands were concerned. After playing the instrument for his mentor, he performed a concert in November of 1920 to an audience of spellbound physics students. In 1921 he filed for a Russian patent on the device.
Theremin: Ether Music and Espionage by Albert Glinsky, 2000, University of Illinois