The Theremin -- Talking About a Spooky Instrument

Today I want to talk about a very interesting electric instrument. The Theremin. Even though many have heard the sound of this instrument, not many people actually know about its existence. Before talking about the instrument itself, let's check out how it sounds. Here is a recording of Somewhere over the rainbow played using a Theremin:

Did you recognize the sound?

A Bit of History

The Theremin was first developed in the 1920's by Russian inventor Léon Theremin (hence the name of the instrument). The Theremin was one of the first electrical instruments. It was therefore quite the invention in the 1920s.

Léon Theremin playing his own invention Image source.

Theremin, an inventor pur sang, was interested in physics at a young age. When he was just 17, he had his own home laboratory where he would do experiments on optics and electrical circuits.

Although famous for being the inventor of the Theremin, he also worked on other infamous devices. One of which was The Thing. A wireless listening device that was used by the Russians to listen to what was going on in the Us ambassador's office. All in all, you can say the Theremin was not just any hobby inventor!

Playing the Theremin,

Alright, let's get back to the instrument itself. As you might have noticed in the video, the Theremin is played without touching the instrument itself! Weird right?

A Theremin by Moog. Notice the antenna and coil on the left and right respectively. Image source.

The device consists of the main housing, a horizontal antenna, and a vertical antenna. The instrument is played by using hand gestures to control the pitch and volume of the sound. In this, the horizontal antenna is used to control the volume, while the antenna is used to control the pitch. By "using" the antennas, I simply mean you move your hands closer or further away from the antenna. This perhaps sounds a bit confusing, perhaps this video will make it more clear:

Working principle

Pretty cool right? An instrument that just responds to your hand gestures! How does that work under the hood? Let me try to explain the basic principle.

The pitch control is using the so-called heterodyne principle. In simple words, this technique can be used to create a new frequency by mixing two different frequencies. Since sound is nothing more than a signal containing certain frequencies, we can use this principle to create the sound of various pitch.

The pitch antenna, that has an output signal with a certain frequency, acts as a variable capacitor. Your hand, while playing the Theremin, acts as a ground plate of this capacitor. Moving your hand to and from the antenna will alter the frequency of the output signal. This output signal is then mixed with a base signal to create the final "mixed" signal that is used to produces the Theremin's distinct sound.

For the volume control a similar principle is used, however instead of mixing the antenna's signal with a base signal, it is directly used to control the volume.

So who is using this thing?

Well, now you know the instrument, you might ask yourself, where is it used? There are a few pop songs that make use of the instrument. A small collection is given here:

Perhaps some of you might say, "Hey what about Good Vibrations by the beach boys?". Well, I too first thought it contained the sound of a Theremin. After doing some research it turns out they used an instrument called a stringer (video with explanation). The reason? Well, it turns out that it was too hard to play the Theremin for Good Vibrations. Here is a recording of the song where you can clearly see they are not using a Theremin:

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Alright, that's it for today! I hope you know know what is generating that spooky 50's Sci-Fy sound when you hear it :)

Have a great weekend!