How does a theremin work?

How does a theremin work?

• A. The performer regulates the frequency with one hand and the amplitude with the other, disturbing electrical fields around protruding bars.
• B. It is played by touching a keyboard to control pitch and volume.
• C. It relies on magnetic tape to generate signals.
• D. It uses breath to modulate airflow through a reed.

Answer: (A)

The theremin works by non-contact control of two separate circuits: hands influence pitch with one antenna and loudness with the other. Inside, two oscillator circuits run at high frequencies; the performer’s hand near the pitch antenna changes the capacitance seen by that oscillator, shifting its frequency and thus the pitch. Meanwhile, the hand near the volume antenna modulates the signal's amplitude, so distance from that antenna sets how loud the note is. The two oscillator outputs are then mixed to produce the audible tone. So moving a hand to change pitch and moving the other to change volume, by disturbing the electrical fields around two antennas, is exactly how this instrument functions. It isn’t played by touching a keyboard, using magnetic tape, or breath and a reed.

The theremin works by non-contact control of two separate circuits: hands influence pitch with one antenna and loudness with the other. Inside, two oscillator circuits run at high frequencies; the performer’s hand near the pitch antenna changes the capacitance seen by that oscillator, shifting its frequency and thus the pitch. Meanwhile, the hand near the volume antenna modulates the signal's amplitude, so distance from that antenna sets how loud the note is. The two oscillator outputs are then mixed to produce the audible tone. So moving a hand to change pitch and moving the other to change volume, by disturbing the electrical fields around two antennas, is exactly how this instrument functions. It isn’t played by touching a keyboard, using magnetic tape, or breath and a reed.