Theremin

Physics:	Electromagnetism, Frequency, Capacitors
Grade Range:	Elementary School, Middle School, High School
Format:	Hands-on, Stage

The Theremin is an original musical instrument created by Léon Theremin in 1928. The Theremin is an exciting hands-on demonstration for kids, and works best in a stage environment if you have made sure to practice playing it.

Materials

• Amp Speaker w/ Cables
  • Audio Cable
  • Theremin Power Cable
• Theremin Box w/ Antennas
• Theremin Stand

Safety Precautions

Please read the General Safety Precautions section of the Demonstration Safety page before performing this demonstration. This demonstration does not require any safety gear, but be sure to follow all setup steps to minimize any damage to the Theremin.

Demonstration

Preparation

1. Set the amp speaker behind (Hands-on) or in front of (Stage) where you plan to use the Theremin, facing outward. Plug in the speaker, and plug the audio cable into the "normal 2" jack.
2. Pull out the stand for the Theremin, and adjust the height for the intended audience. unfold the feet on the stand and set it in front of (Hands-on) or behind (Stage) the amp speaker.
3. Pull out the Theremin, and carefully screw it onto the stand. You want it to be snug, but not tight.
4. Attach the antennas to the Theremin. Looking at the front of the Theremin, the straight antenna goes on the right, and the curved antenna goes on the left.
5. Pull out the power cord for the Theremin and plug it into the rear port. Plug the audio cable into the front port on the Theremin.
6. Turn on the speaker. Set the volume knobs on the speaker between 2 and 3. After the speaker has warmed up for 1-2 minutes, flip on the "ground" switch.
7. After turning on the "ground" switch, wait 20-30 seconds before flipping on the on/off switch on the Theremin.

Presentation (Stage)

• Note: the following steps are written with the assumption that the presenter has already familiarized themselves with the Theremin. Like any musical instrument, you have to familiarize yourself with it in order to use it effectively.

1. Prior to the start of the show, adjust the "volume" and "pitch" knobs as needed to tune the Theremin for you to use. Leave the "waveform" and "brightness" knobs at 50%. Leave the Theremin off so to not spoil the surprise.
2. Ask the audience if anyone recognize the device you have in front of you. If any do, see if they can name it. Explain some of the history behind the Theremin.
3. Turn on the Theremin, and show the audience that you can make noise using it. After playing with it for 15-20 seconds, quiet the Theremin and ask the audience for ideas on how you are controlling it. You are not touching the device, but they can hear the sounds being made as you move you hands!
4. After taking some ideas, introduce electromagnetism and electromagnetic waves. Show that the distance between the antennas and your hands determine the pitch and volume.
5. For an older audience, ask if they know of capacitors and alternating current. If any do, get ideas from the audience. Introduce capacitors, and explain how your hands and the antennas are acting as capacitors.
6. If you have practiced a song, play it for the audience! You can also generate sounds that the audience will likely recognize as "alien" or "outer space" noises.

Presentation (Hands-on)

1. Prior to the start of the show, adjust the "volume" and "pitch" knobs as needed to tune the Theremin for use. Leave the "waveform" and "brightness" knobs at 50%.
2. When students come up, show them how to hold their hands near the Theremin. Let each student try playing it, making sure they take turns with it.
3. As able, explain how the distance of their hands to the antenna creates the difference in pitch and volume. For extra curious minds, feel free to include some fun facts about the inventor, Léon Theremin.

Why This Works

The Theremin is an electromagnetic instrument. Electromagnetism is the study of electricity, light, and magnetism. For this demonstration, we are looking at electricity, and how this weird instrument can be played without being touched! When you move by the vertical antenna, you hear the pitch change. When you move by the horizontal antenna, you hear the volume change. These changes happen when the Theremin detects a change in frequency. Frequency in electromagnetism is a count of the number of waves per second. When the Theremin is on, it is constantly sending electromagnetic waves out from the antenna. If something conductive is near the antenna, such as your hand, then the waves bounce back at the antenna, which the Theremin detects. When you move your hand closer, the waves bounce off of it sooner, and the higher the frequency the Theremin detects. For the vertical antenna, a high frequency means a high note, and a low frequency means a lot note. For the horizontal antenna, a high frequency means a low volume, and a low frequency means a high volume.

The Theremin detects these changes in frequency because it behaves similarly to a capacitor. Capacitors are when you have two conductive surfaces near each other with a non conductive material between them. This space between the conductive surfaces can be used to store charge. In this case, the first conductive surface is the antenna, and the second conductive surface is you! When you move near the antenna, you are adjusting the capacitance, or the amount of space to store charge between you and the antenna. As you move closer, the space becomes smaller, and the potential amount of charge stored becomes smaller. This change in capacitance is what changes the frequency that the theremin detects. By decreasing the capacitance, the frequency increases.

Additional Information

• Léon Theremin has a colorful and exciting history behind him. He was a Russian physicist and inventor who gave shows with his all electric instruments in the 1920's and early 1930's. He was kidnapped by the KGB in the 1930's, brainwashed to work as a soviet spy, and worked on movement detection and sound recording technology for them until the 1960's. In the 1970's he became a professor at Moscow State University, and he continued to build and present his Theremins and other electric instruments until he passed away in 1993, at the age of 97.
• This demonstration pairs well with the Flame Tube and the Musical Pipes. It can also be paired with the Tesla Coil.