What this virtual theremin is
This page is a virtual theremin. You play it by pressing on a pad and moving, and the position of your pointer or finger decides the sound. Moving sideways changes the pitch across three octaves, from C3 to C6, and moving up and down changes the volume. There are no keys or strings, so the pitch glides smoothly, which gives the instrument its famous eerie, singing sound. Nothing needs installing and no account is required.
The sound is generated in your browser using the Web Audio system, so no audio files are downloaded. It copies the idea of a theremin, but it is a simplified imitation and not a recording or an exact model of one.
How a real theremin works
The theremin was invented by the Russian physicist Leon Theremin, who patented it in the 1920s. It is played without touching anything. The instrument has two metal antennas. Your hand changes the electrical field around each antenna, and the instrument turns that change into sound. Moving a hand toward the pitch antenna raises the note, and moving the other hand toward the volume antenna lowers the loudness.
The result is a pure, gliding tone with no frets or keys to define notes, so the player has to find each pitch by ear and by feel, which makes the instrument hard to master. Theremins became well known through the soundtracks of science-fiction films in the 1940s and 1950s, and they are still used by experimental and rock musicians. The Lithuanian-born player Clara Rockmore became the best-known virtuoso of the instrument, and her recordings show how precise and expressive theremin playing can be.
How this version maps your movement
On a screen, there is nothing to wave a hand at, so the pad stands in for the two antennas. Horizontal position sets the pitch and vertical position sets the volume. The pitch scale is exponential, like a real instrument and like a piano, so each octave takes the same width: C3 is on the left edge, C4 and C5 are a third and two thirds of the way across, and C6 is on the right edge.
The faint vertical lines on the pad mark each semitone, and the stronger lines mark every C. A readout below the pad shows the nearest note, how many cents sharp or flat you are, the exact frequency and the volume. One hundred cents make one semitone, so the readout helps you learn how close you are to a true note.
Playing with a mouse, touch screen or keyboard
- Mouse. Press and hold on the pad, then drag. The sound follows your pointer, even if it leaves the pad, and stops when you release.
- Touch screen. Touch and hold on the pad and slide your finger. Only one finger plays at a time, as the instrument is monophonic. The pad does not scroll, so scroll the page from outside it.
- Keyboard. Press Tab to focus the pad. Space or Enter starts and stops the sound, the left and right arrows move the pitch by a semitone, Shift with an arrow moves by an octave, and the up and down arrows change the volume.
The keyboard controls move a marker even when the sound is off, so you can set a note before you start it.
Snap to notes, vibrato and tone
Playing a theremin in tune is difficult, so this page offers Snap to notes. With it on, the pitch jumps to the nearest semitone, so every position gives a clean note and a slide steps up and down the scale. With it off, the pitch follows you exactly, which is how a real theremin behaves.
Vibrato is a small, regular wobble in pitch. Real players make it by shaking the hand, and it is a large part of the theremin's expressive voice. The slider sets its width in cents. The Tone buttons change the wave: sine is the purest and closest to a theremin, triangle is slightly brighter, and saw is buzzy and sharp.
Beginner exercises
- Find the glide. With snapping off, press at the left edge and slide slowly to the right, listening to the pitch rise.
- Control the volume. Hold one pitch and move up and down to fade the sound in and out.
- Find C. Turn on Snap to notes and try to land on the strong lines that mark each C, using the readout to check.
- A simple melody. With snapping on, try to play a short phrase of three or four notes and repeat it.
- Add expression. Turn snapping off, set vibrato to about 20, and hold a long note while you slowly bend it a little higher.
What a virtual theremin is good for
A virtual theremin is a fun way to explore pitch, because you can hear continuous pitch and the way notes live on a scale. It suits students learning how frequency and volume relate, children who enjoy a sound toy, and creators looking for a spooky effect or an unusual lead sound. Compare it with the online synthesizer, which plays fixed notes with a keyboard, and with the virtual violin, another instrument with continuous pitch. It also works well as a listening exercise: close your eyes, slide slowly, and try to name each note you pass before you check the readout.
Online theremin versus a real one
A real theremin responds to the tiniest movement of your hands in the air, with no contact and a very fine control of pitch and volume. Players spend years learning the instrument, and its response depends on the room and the player's body.
The virtual one uses a screen, which gives you a visible scale and a readout to learn from, but the control is coarser, and a mouse or finger on glass is quite different from a hand in air. Consider it a toy and a teaching aid for the idea, not a substitute for the real instrument.
Limitations of this version
- The sound is a simple synthesized tone and is not a model of any real theremin.
- Only one note can sound at a time, and only one finger is used.
- The range is three octaves, from C3 to C6, and cannot be changed.
- On touch screens, the pad captures touch, so the page cannot be scrolled from on top of it.
- Nothing is recorded or saved, and there is no MIDI input.
Common problems and how to fix them
- No sound. Browsers keep audio off until you interact with the page, so press on the pad first. Then check the volume slider, your device volume and the tab's mute icon. On an iPhone, also check that the silent switch is off.
- The sound is very quiet. The bottom of the pad is silent. Move toward the top for a louder sound.
- The page will not scroll on my phone. The pad blocks scrolling on purpose. Touch above or below it to scroll.
- The pitch is hard to control. Turn on Snap to notes and use the readout to check where you are.
- The sound lags. Close heavy tabs and use wired headphones or the device speaker.