Hack old devices to create weird sounds, and invent unusual controls for your own computer compositions.

So far in this book, you’ve learned how to change the sound produced by an instrument—at least for acoustic instruments. Acoustic instruments produce sound waves when they vibrate. Change the size, shape, or material the instrument is made out of, and the instrument will vibrate differently. Build an instrument that’s big and heavy, and it will vibrate slower and produce lower notes. Build it small and light, and it will vibrate faster and play higher notes. If you make it out of wood, it will have overtones that add richness to the tone. If you make it out of metal, it will play a sharp, clear note.

But as you’re about to discover, some instruments don’t follow the rules. Electronic instruments (which fall into the category of electrophones) create vibrations using electrical signals. And those electrical signals can be shaped to produce different notes and tones, in the same way the body of an acoustic instrument shapes sounds. An instrument that generates electrical signals and shapes them to produce musical sounds is called a music synthesizer. (Synthesize means “put together.”)

Music synthesizers have been around for over a century. In the late 1890s, an instrument called the telharmonium sent musical tones in the form of electrical signals over special phone wires. In the 1920s, the theremin made music using radio waves. By the 1960s, synthesizers got smaller and easier to use. Today, synthesizers (or synths for short) are used in all kinds of music. They can create drumbeats, crazy harmonies, and otherworldly sounds. And electronic instruments can be programmed like computers to play certain sounds, patterns, or even entire songs. In fact, music software can turn your computer into an instrument!

Some electronic instruments look a little like acoustic instruments. They may have keyboards like a piano, strings like a guitar, or a mouthpiece like a wind instrument. In addition, they may have a control panel filled with switches and knobs that let you modify the sound in endless ways. But electronic instruments can take all kinds of interesting and artistic forms. The only thing that matters is what electrical components are connected to them.

In this chapter, you’ll get to play around with electrical circuits and explore ways to produce strange and wonderful sounds with everyday devices.

Where Electronic Music Gets Its Spark

How does an electronic instrument produce sound? When you play an acoustic instrument and cause vibrations, you are making tiny air molecules shake back and forth. Areas of high pressure (with lots of molecules packed in) and low pressure (with fewer molecules spread out) travel away from the instrument in waves. These pressure waves carry the sound energy from the instrument through the air to your ears.

Synthesizers create similar pressure waves using electricity. Electricity is the flow of energy in the form of electrons, which are particles found in atoms, the building blocks of molecules. A synthesizer usually contains some kind of generator that causes electrons to vibrate. The term for vibrations in electrons is oscillation. Oscillation creates pressure waves that can be used to power speakers or earphones that translate the electrical energy into sound waves you can hear. The measure of the pressure of electrons in a system is its voltage.

To shape the electric signals and produce different sounds, synthesizers use several techniques. One is to generate multiple signals and blend them to produce new patterns. Remember how a sound wave interferes with itself when it bounces back from the end of an instrument? Waves of different frequency can be electronically added together in the same way. Another technique used by synthesizers is to filter some of the harmonics that make up a tone. Making different overtones stronger or weaker can change the timbre of a sound.

Just like with sound waves, you can use drawings called waveforms to represent how electrons oscillate. The line of the waveform goes up and down to show you changes in voltage over time. The shape of the waveform can tell you what the timbre of the sound is like. Here are some types of waveforms you can generate on a music synthesizer:

The Buzz about Synthesizers

A synthesizer is made up of several different electronic components that serve different functions. They can all be built into one unit, or you can connect separate modules together. The sound is created by generators, then shaped by modulators. Amplifiers make the sound louder or softer, and speakers turn the electric signals into sound waves that you can hear. Here are some common synthesizer components:

The Strange and Mysterious Theremin

The theremin is one of the strangest kinds of electronic instruments. It consists of a box with two antennas. A loop-shaped antenna that comes out of the side controls the volume. The other antenna is a stick that stands straight up and controls the pitch.

Playing it is even stranger. Once you turn the instrument on, you never touch it. Instead, you control the sound by waving your hands closer and farther away from the antennas, opening and closing your fists. Shaking your hand makes the pitch wobble up and down. Watching someone play the theremin is like watching some kind of upper-body dance or martial art exercise, full of fluttering and graceful movements.

The theremin has a unique and strange sound, too. Very few people are able to master the techniques needed to play it as a classical instrument, as it was designed. You’re more likely to have heard it creating an eerie mood in old science fiction movies. Its spooky whistles and squawks sound a lot like the human (or alien) singers. It has also been used in rock music. That high-pitched voice singing “ooh-OOH-ooh, ooooh ooh” in the Beach Boys song “Good Vibrations” is actually a theremin!

If you’ve ever walked near a radio while it was playing and noticed a change in the sound—it gets louder, softer, or even squeals—you’ve experienced what happens when you play a theremin. A theremin works by creating interference between two radio waves. When the two waves mix, they combine and produce a new frequency, which you hear as a note. The pitch of the note is the difference between the two frequencies. Your body has its own, very weak, electrical field. So the closer you get to a device that’s producing electrical waves, the more your electrical field affects those waves. That’s how you can control the pitch of a theremin without even touching it!

Project:
DIY Theremin

A theremin uses oscillators to create electrical waves, but you can make a simple version using ordinary radios. This project was adapted from instructions by sound artist and musical inventor Yuri Suzuki and Phil Borell. Old-fashioned radios work best for this project, so scour your attic, garage sales, or thrift shops for models from 20 or 30 years ago. See the Materials list for details on what to look for.

1. Before you make any changes to the radios, see how they affect each other just by tuning them to specific frequencies. When you tune in a station, you are actually adjusting the radio to pick up a certain radio wave frequency. The frequency is measured in kilohertz (written as kHz) for AM stations or megahertz (MHz) for FM stations. (Now you know why radio stations often use numbers as part of their name such as “FLY 92” or “KISS 106”—the numbers tell you their frequency!) The DIY Theremin uses the radios like this:
   • The first radio is a receiver. This is the only radio that you will hear.
   • The second radio is a fixed transmitter. Once you get it tuned to the proper frequency, it will cancel out the sound coming out of the receiver.
   • The third radio is the variable transmitter. By moving the frequency on this radio up and down with your body, you will change the pitch of the sound coming out of the receiver. Right now you will use this radio as is, but later on you will add an antenna (or use its antenna if it has one) so you can control it just like on a real theremin. To do this, the radio you use for a variable transmitter should use a rotating dial as a tuner and be easy to open up (by removing screws or by carefully prying it apart).
2. Here’s what to do with the three radios:
   • Take the radio you are using as a receiver, turn it on, and set the tuner to 1500 (which tells it to pick up a frequency of 1500 kHz). Turn up the volume. If you can hear talking or music, try going up the dial (raising the frequency) until you hear mostly static, that scratchy noise between stations.

     

     

   • Turn on the second radio, the one that will be your fixed transmitter, and lower the volume until you can’t hear it at all. Set the tuner to a frequency that is 455 kHz below the station on the receiver radio. In other words, if your receiver is set at 1500, set the fixed transmitter at about 1045 (1500 – 455 = 1045). If the receiver is set at 1600, the fixed transmitter should be set at 1145. Hold the fixed transmitter right next to (or even on top of) the receiver. The static should disappear and the receiver should go silent. If it doesn’t, try adjusting the frequency on the fixed transmitter until you get as little sound as possible from the receiver.
   • Turn on the third radio, the variable transmitter, and lower the volume until you can’t hear it at all. Set the tuner to the same frequency as the second (fixed transmitter) radio. Hold the variable transmitter radio near the first two radios. Instead of silence, you should hear a whistling sound that changes as you move it closer and farther away. Put the variable transmitter radio down near the other radios and see how moving your hand around it affects the pitch. Then try changing the frequency with the tuner slightly to change the pitch. If you want, you can stop here and use your theremin as is. But if you want to add an antenna, go on to the next step.
3. To alter the variable transmitter so you can play your DIY theremin using an antenna, first tune it to an AM station until you can hear talking or music. Then, carefully open up the radio. You may have to remove some screws (which may be hidden underneath the batteries) or carefully pry the back off. Avoid breaking any wires, especially any that connect the front and the back.

   

   

4. Look for the plastic box that surrounds the tuning dial. On the back of the box (or on the circuit board it is attached to), near the corners, there should be four screws or blobs of silver solder (the melted metal used to connect components to circuit boards). One of these is the capacitor terminal, the component that tunes the radio to AM stations. Touch each blob with a small screwdriver until you find the one that makes the station more staticy and harder to hear. When you find the capacitor terminal, stick one end of a piece of foil tape or wire to it. The tape should be a few inches long, but thin enough to avoid touching anything else besides the terminal. Carefully close the radio back up.

   

5. Make an antenna and a stand that will hold it upright. A piece of stiff wire stuck into a cork and attached to a piece of cardboard is fine. Attach the other end of the foil tape to the antenna. If there already is an antenna built in, attach the other end of the tape to that.
6. Stand the homemade antenna next to the variable transmitter radio. Tune it to the original frequency (the same as the second, fixed transmitter, radio). Use the tuning dial to adjust it until you hear the whistling tone again. Try to get the lowest pitch you can. Then slowly wave your hands around the antenna to see how many notes you can produce. Wiggling your hand creates a wobbly vibrato. What other effects can you get out of your new theremin?

Project:
littleBits Synth Glove

The littleBits Synth Kit is made up of small, snap-together magnetic parts that can be arranged in different combinations to create a real working music synthesizer. It’s based on the Korg MS-20, a synthesizer that was first introduced in 1978. The Synth Kit lets you shape sound waves, control them with switches and sensors, and even program repeating patterns. And the kit is powered by a 9V (9 volt) battery, so it’s safe to take apart and put together.

All the elements of a basic synthesizer are found in the kit:

• Signal generators (two oscillators and a random voltage generator)
• Controllers (a keyboard and a sequencer)
• Modulators (an envelope that controls how quickly each note gets louder and softer, and a filter that lets you adjust the balance of high frequencies and low frequencies)
• Modifiers (a delay that controls how much echo a note produces, and a mix module that combines sounds from two sources and sends them to the speaker)

You can connect the modules in multiple ways to create an endless variety of sounds. And each of the modules has knobs, dials, and switches that let you adjust the settings to your taste. Best of all, you can add other kinds of littleBits modules and attach them temporarily to creations you build using crafts materials or even your clothing to make your own synth-based musical inventions!

The littleBits Synth Glove makes it possible to play different notes and phrases with a wave of your hand. It was inspired by the Musical Glove invented by Imogen Heap (see the “Musical Inventors: Imogen Heap” sidebar that follows this activity).

1. First build the synth circuit. The circuit has two rows. The top row uses the Micro Sequencer to play a repeating series of four notes as background. The bottom row creates a variable tone that you will control with your glove. Both rows start with an oscillator to generate the sound wave frequency. Then they add other modules to get a more interesting sound. Finally, they are blended together with the Mix module and sent to the speaker, which converts the electrical signal to a sound wave. (See Chapter 5 to find out how speakers work!) Start by building the top row using the following modules:

   Power>Split>Micro Sequencer>Oscillator>Delay>Mix>Filter>Synth Speaker

   

   

   

   Next, build the bottom row. Take the extra wire on the Split module and add the following modules. At the end, connect the row to the extra wire on the Mix module.

   (Power>Split)>Oscillator>Envelope>(Mix>Filter>SynthSpeaker)

   

2. Now you can create some music, beginning with the background sound. To create the background rhythm that will repeat over and over, set the tiny switch on the Micro Sequencer to “clock.” Tune the Sequencer to play different notes by adjusting the four knobs. Choose the speed with the little dial. To change the timbre, play around with the Delay module, or swap it out for another one. The other row of modules produces the variable note. Tune it to a note that sounds good with the background rhythm. This is the tone that will be controlled by the glove.
3. When you like the way your synthesizer sounds, it’s time to add the main layer of sound. Adjust the modules on the second row using all the knobs, dials, and switches until you get a note that sounds good with the background rhythm.
4. When you’re happy with both layers of sound, insert the Wireless Receiver module between the Split wire and the Oscillator. Make sure it is set to the same channel as the Transmitter. Use the middle connector on the right side (number 2). You can turn off this circuit while you build the glove controller.

   

   

5. The glove controller lets you play your synth by moving your hand around. It varies the voltage according to the amount of light shining on it, and it will work even if you are standing on the other side of the room from the synth, up to 100 feet (30 m) away! Make sure the Wireless Transmitter is set to the same channel as the Wireless Receiver and use the middle connector on the left side (number 2). The circuit should look like this:

   Power>Wire (you may need two, attached end to end)>Light Sensor>Wireless Transmitter

   

   

6. To attach the Light Sensor circuit to the glove, you’ll need to use the hook-and-loop shoes. They also help keep the modules connected to each other. Snap the shoes over the feet where the modules meet. Snap the third shoe onto the other foot on the Wireless Transmitter. Cut a piece of hook-and-loop tape long enough to fit all three shoes. Press the pieces onto the hook-and-loop strip until they are firmly attached, leaving the paper on. To position the tape, put on the glove and make a fist. Peel off the backing paper and stick the tape onto the back of the glove so the top of the T shape goes across your knuckles. Press it firmly in place.
7. Now play your musical glove! Turn on your synth and let the rhythm start going. Turn the glove circuit on, and slip the battery into a pocket, where the wires won’t get in your way. Then stand in a spot where you can wave your hand in and out of the light. How does the sound change? Can you control the pitch, the volume, or the timbre?

Troubleshooting tips:

• If either of your circuits isn’t working, check to see that all the modules are connected properly. The Wireless Transmitter and Receiver have on-board LED indicator lights that show you when they are getting power from the battery.
• If you don’t get a lot of variation in sound as you move your glove around, use the little plastic screwdriver that comes with the sensor to adjust the sensitivity screw.
• If there’s not a lot of light around, try switching the sensor to “dark” instead of “light” and let it measure different degrees of darkness.
• The Light Sensor may work better if you use an LED light source or direct sunlight coming in through a window.
• Use fresh 9V batteries—the Wireless modules seem to burn them out fast.

Extensions and adaptations:

• Try adding different kinds of sensors instead the Light Sensor. How can you make the sound of the synth change by bending a finger or clapping your hands?
• Find tips on how to record, edit, and share your music at littleBits.cc/recordyourmusic.

Project:
Makey Makey Musical Surface

One of the fun things about electronic instruments is that they don’t have to look anything like “normal” instruments. They don’t even have to look like the control board of a synthesizer, with knobs and buttons. In fact, you can use anything, including drawings or other kinds of art, to trigger electronic sounds. All you need is something that can control an electrical circuit to produce a sound. That means you can turn ordinary arts and crafts into music synthesizers!

One easy way to do that is with a Makey Makey invention kit. Makey Makey was created by inventors Jay Silver and Eric Rosenbaum when they were students at the MIT Media Lab. It is an Arduino-based microcontroller board that plugs into your computer and acts like a second keyboard. (There’s also a smaller version called Makey Makey GO that has one key.) The Makey Makey board has six metal pads marked up, down, left, right, space, and click on the front, and places on the back where you can plug in wires to create even more keys. When you connect something conductive to a key on the Makey Makey, it triggers that key—just as if you had pressed it on your computer keyboard. When you use it with Scratch (a free online programming language for kids created by MIT) or with other music software, it lets you turn unusual objects into a synthesizer.

This project shows you how to use Makey Makey and a remote control car to create a musical playing surface. Try it out, and then let it inspire you to invent a musical controller of your own!

1. First, make the playing surface. Cut the aluminum foil tape into strips, one for each key that you want to connect to a note. You can trim the tape into interesting shapes if you like. Then fold over one end, with the protective paper on the inside. This will be the tab that hangs off the board so you can clip the Makey Makey’s wires onto the conductive areas. Peel back the protective paper on the folded end of the tape to expose the glued side. Press it so the glued sides stick to each other. If you need to, trim off any of the glue that is sticking out.
2. Attach the first strip anywhere along the edge of the board with the tab hanging off. Slowly peel off the rest of the protective backing while smoothing the tape down on the cardboard. Repeat with the other strips—making sure that none of them are touching. You may also want to test the RC car to make sure it can drive around the board without getting stuck.

   

   

   

3. Now connect the Makey Makey to the computer by plugging the cord that comes in the kit into a USB port. You do not need any other software or drivers. The lights on the board should go on. To test the “keys” on the front of the Makey Makey, touch the metal Earth bar along the bottom edge of the board with one hand, and touch one of the metal pads for the keys with the other. You should see the light next to that key light up. If it doesn’t, check the troubleshooting tips at the end of this activity. To see how the Makey Makey triggers a note, go to www.makeymakey.com, click on the Apps page, and try the piano or one of the other sample music apps. The Makey Makey will work with any program that uses the keys on your computer keyboard.

   

4. Next, test the playing surface to make sure it works with the Makey Makey. Clip one of the alligator clip wires that come with the Makey Makey into one of the keys on the board. The jaws of the clip fit into the holes on the board. Clip the other end of the wire onto the tab for one of the strips. Touch the Earth bar and one of the foil strips. The key should trigger, just like when you touched the board itself. Check the troubleshooting tips at the end of this activity if you need help. Do the same with all the other foil strips on the playing surface.

   

   

5. It’s time to connect the RC car. Fold under the end of a new strip of foil tape. Attach it to the back of the car to make a tab that drags along the ground a little. The bottom tab needs to touch the conductive strips on the playing surface without getting stuck or coming off. The foil strip should be long enough to fold into another tab at the other end that sticks up. The top tab needs to keep the wire you will connect to the car away from the playing surface so it doesn’t get tangled. Connect a wire (extra long if you have it) to the top tab. Connect the other end of the wire to the Earth bar. If your wire isn’t long enough, connect two alligator clip wires together by snapping the metal teeth of one over the metal teeth of the other.

   

   

   

6. Now that your musical surface is working, you need something to play! The Apps page on the Makey Makey website has links to online instruments you can try. (Some of them are listed in the following “Music Software for Your Makey Makey” sidebar.) You can also use any computer program or website that uses the arrow keys to make sounds. And to really have fun, check out programming languages like Scratch and other software that lets you write your own music. Here are some ideas for how to use them:
   • Use the keys to play individual notes in a scale or the notes of a song.
   • Use the keys to play a phrase made up of multiple notes.
   • Record your own samples or upload music or sounds and shape them using the music software.
   • Use one or more of the keys to shape the sound of the other keys, such as by changing the timbre or the pitch. For example, on Scratch, you can play notes that sound like different instruments by plugging the number of the instrument into the program. If you write a Scratch script (program) that tells it to add 1 to the number each time, you’ll get a different instrument every time you hit that key.

Troubleshooting tips:

• Don’t forget that you must connect to both a key and the Earth bar to activate a note.
• If you don’t get a sound when you touch the Makey Makey keys or foil strips on the musical surface with your fingers, your skin may be too dry. Use hand cream to moisten it.
• If two notes sound at the same time when only one is triggered by the RC car or your finger, then there is a short circuit connecting them. Look for any place the foil strips may be touching. There should be space around every strip.

Adaptations:

• To create a musical playing surface with a Makey Makey GO (which only has one key), use Scratch or other music software to write a program that plays a song segment by segment, or that generates random notes every time it is triggered.
• If you don’t have an RC car, you can play the surface with your hands by attaching the grounding wire to the cuff of your shirt or a bracelet. Make sure that it touches your skin. Or make a pointer out of conductive material (such as aluminum foil) that you can use to activate the keys.

Extensions:

• Hide the tangle of wires connecting the surface to the Makey Makey by building it into or on top of a cardboard box base.
• To get rid of the Earth wire attached to the RC car, put a strip attached to Earth next to (but not touching) every one of the strips that activate the keys. Then the strip attached to the car (or even foil wrapped around the wheels) will act like a bridge to connect the two strips and activate the key.
• Experiment with other ways to make a musical playing surface. What about a bumpy design made with conductive modeling dough? (Don’t let the lumps of dough touch, or separate them with non-conductive Plasticine clay.)
• Decorate the RC car, or build a cover for it to go with the theme of your playing surface. For instance, you can make it look like a hand and have it drive around a surface that looks like a piano keyboard. Or go wild and turn it into a cloud that floats across a surface that looks like the sky, or a mermaid that “swims” around an underwater scene.

The Silly Science of Circuit Bending

Circuit bending is a goofy way to create musical sounds. You take an electronic device—usually a singing doll or a toy that talks—and rewire the insides to change the way it sounds. The random squeaks and noises can then be used to create electronic music. Taking a prerecorded sound and distorting it to create something new is called sampling. In a synthesizer, samples are used just like other kinds of sounds. You can modify a sample by playing it faster or slower, which makes the pitch go higher or lower. You can also trim it into shorter pieces, loop it around over and over, or play it in reverse. Some musicians even play circuit-bent instruments live in concert.

Musical Inventor Reed Ghazala (anti-theory.com) is known as the “father of circuit bending.” As a teenager in 1967, he accidentally short-circuited the amplifier from a toy by touching it to his metal desk and it started to squeal. He began adding knobs and switches to turn toys into toy-shaped music synthesizers, and his creations became prized by top rock musicians. That started a musical maker movement that is still popular today. However, modern talking or musical devices use miniature components on printed circuit boards, which are harder to rewire. So circuit benders are always on the lookout for old toys that still have components like resistors they can remove and replace to create their own inventions.

Project:
Simple Circuit Bending

There are some quick and easy ways to play around with circuit bending on modern circuit boards that let you create different kinds of sounds. It’s harder to use these as synthesizers, because they won’t make the exact same sounds over and over when you them want to. But you can record the sounds you produce and use them with sampling software. (See the Makey Makey Musical Surface project for software suggestions.) And they’re fun to experiment with!

1. Open up the greeting card. The prerecorded music should start to play. (You may want to make a video or audio recording of the music to help you remember what it sounded like before you started to “bend” it.)
2. The first thing you need to do is make your own switch so you can turn the music on and off while the card is open. Pry open the glued flap inside the card to expose the circuit board and speaker. Look for a little plastic tab that slides in and out of the circuit as you open and close the card. This tab separates a metal clip from a metallic pad attached directly to the card. The metal clip is attached to a battery. (There may be more than one battery on your card.) It acts like a drawbridge that lets electricity flow across it to make the sound play. When the clip is up, the circuit is open and nothing happens. When it comes down and touches the pad, it closes the circuit and the sounds start to play. Remove the tab and replace it with a piece of paper, or cut off the tab with a piece of the card attached as a handle.

   

3. If you want, use the card (or another piece of stiff paper) to make a little stand. (To protect the wires coming out of the speakers, which can snap off if they are bent, cover them with a little hot glue or soft-drying flexible clay.) Fold the card so the speaker is standing up to make it easier to hear. Punch some holes on the paper behind it to let more of the sound out.

   

   

   

4. To circuit-bend the card, you need to connect parts of the circuit that are not usually connected. The best results come from connecting components on the boards to a battery. To do this safely (and to avoid frying the components), you need to reduce the electric current that flows between them. A variableresistor lets you control the amount of electricity that can flow between two points on a circuit. The lead in a pencil (which is actually made of a soft, black substance called graphite) can conduct small amounts of electricity. That means you can use a pencil line as a variable resistor. Just take an index card and scribble a thick, heavy line along three of the edges (see Figure 4-52). Make sure there are no gaps where the pencil lines are connected. Clip one of the wires to one end of the line. Clip the other wire to the other end of the line. The farther apart the wires are along the line, the higher the resistance is between them.

   

   

   

   

5. Next, clip the free end of one of the wires to the metal clip that connects to a battery on the card. Use the free end of the other wire to touch different components on the circuit board. Try any interesting areas you can find. One spot to look for is a tiny rectangle marked “R,” which is a resistor. You may also see other markings that show where there are other components, like capacitors, or where the speakers are attached. While you are poking around, turn on the music. If the volume or the speed of the music changes, you have found a good circuit bending point! Make a note of where it is and what happened. If you have a camera, take a close-up photo of the spot to help you remember, or shoot a video to demonstrate what happens. You can also try varying the electricity by moving one wire on the pencil variable resistor a little closer to the other wire.

Extension:

• Try circuit bending battery-powered toys that make noise. Spelling toys, toy electric guitars, and talking dolls are all favorite targets for circuit benders. Look for them at garage sales and thrift shops. Here are some ideas for what to do with them:
  • Swap in a solar panel for the batteries and control the speed that way. You can remove the solar panel from an old garden light, making sure to keep the wires that are attached to it. Then remove the batteries from the toy, and connect the positive and negative terminals to the solar panel wires.
  • Control the speed by using a variable resistor (like a photo sensor that varies with the amount of light shining on it) to bypass the on/off switch.