Play the Theremin: How The Theremin Works

How The Theremin Works

A quick guide to how the theremin works

"With this instrument, I have made it possible to produce tones of constancy of pitch not even remotely approached by the best piano or organ".
-Leon Theremin, 1927

There were, and still are, two distinct schools of thought in the theremin world. One says the theremin, far from being a novelty, is such as serious as, and no different to any other classical intrument, and it was Clara Rockmore who established the level of artistry required to gain the instrument acceptance. The other, including composers such as Varese and Cage (as in his 'Variations V'), rejoices in the aural 'novelty' aspect of the instrument, using it's unique means of expression and timbre to create new modes of music radically different to those which have gone before.

'By using an alternating current of suitable frequency, tones of varying pitch are easily obtainable. A small vertical rod is used as the antenna. When the instrument is in operation, electro-magnetic waves of very weak energy are generated around this rod. These waves are of a definite length and frequency. The approach of a hand, which is an electrical conductor, alters the conditions in the electro-magnetic field surrounding the antenna, changes its capacity and thus affects the frequency of the alternating current generated by the apparatus. In this manner, a kind of invisible touch is produced in the space surrounding the antenna, and, as in a cello, a finger pressing on a string produces a higher pitch as it approaches the bridge, in this case also, the pitch increases as the finger is brought nearer the antenna.

Likewise the intensity of the tone can also easily be changed by a simple movement of the hand in space. For this purpose the instrument is equipped with another, in this case circular, antenna around which electro-magnetic waves are similarly formed. The approach of a hand toward this antenna causes a change in the degree of the intensity of the alternating current which produces the tone. Thus by raising the hand over the ring-shaped antenna the note sounded grows louder and by lowering the hand it grows softer, until it dies out in the softest pianissimo.' -Leon Theremin

The theremin is best thought of in terms of a 'sensor' device, that functions along the same lines as a metal detector. It works by sensing the proximity of the player's hands to the antennas. How does it do this? By sensing the electro-magnetic field around each antenna. However, the theremin is incapable of distinguishing between the hands or any other part of the thereminist's body - or for that matter, any other people or objects inside the field's range.

Therefore, for the performer to produce music of any accuracy on the theremin, it is essential to maintain a good (i.e. balanced) posture, and to keep other parts, such as the head, still at all times. This places great demands on the thereminist.

The theremin's sound is produced by the electronic principle of 'heterodyning' - when the frequency of the 'pitch' oscillator is subtracted from the frequency of a fixed oscillator, the resultant frequency produced falls within the range of human hearing, and this is what we hear through a speaker as sound.

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