Concepts

AC circuits, sound, frequency

Overview

Theremins are played by moving your hands near (but not touching) two antenna. One antenna controls pitch, the other controls volume. Theremins work by creating two AC currents using two capacitors (one for pitch and one for volume). The capacitors are unusual in that one "plate" is an antenna, and the other is your hand. The distance between the "plates" (i.e. the antennae and your hands) determines the frequency of the AC currents. The AC currents are modified by internal electronics to combine the pitch and volume components, convert the pitch into a frequency audible to the human ear, and amplify the sound. The resulting signal is sent to speakers.

Details

Equipment

• [1] Theremin
• [1] Pair of speakers
• [1] 3.5 mm stereo to 1/4" mono adapter
• Extension cord (if necessary)

Classroom Assembly

1. Before plugging in the theremin, attach its antennas, with the U-shape on the left and the straight line on the right.
   
2. Place theremin on top of lectern shelf and plug it in.
3. Connect the speakers to the "audio out" port using the stereo to mono adapter.
4. Plug in the speakers.

Script

1. Turn on the theremin and speakers.
2. Control the pitch of sound by moving your hand near the upright antenna. Moving your hand closer increases the pitch. You can produce vibrato by vibrating your hand.
   
3. Control the volume of sound by waving your hand near the loop antenna on the side of the theremin. Moving your hand away increases the volume.
   
4. Try to play a song!

Additional Resources