Build a Diddley-Bow Stringed Musical Instrument
To build a basic diddley-bow in this do it yourself activity. The diddley-bow is an instrument much older than a viol, harp, or lute- it is a modification of a stringed instrument from West Africa.
Easy (8-14 year olds)
Easy with help (6-8 year olds)
Kids younger than 6 can have fun experimenting with a pre-made diddley-bow.
Download and Print (PDF): How to build a Diddley-Bow string instrument
A long narrow board
Wire or string
Nails or screws
A small piece of wood or metal
Two tin cans of different diameters
To build a basic diddley bow, connect a single piece of wire to two screws mounted on either end of your long board. Insert a tin can near one end of the string to act as a bridge (you could use a glass jar, but be careful that you don’t break it when you tighten the wire).
Play it by plucking the wire or string with one hand, using your other hand to move the glass jar or tin can along the length of the string to adjust the vibrating length.
Musical instruments have existed before humans had a written language. Scientists have discovered flutes made from bird and mammoth bones and have placed their origin as being around 43,000 years old, through carbon dating.
Flutes, drums, and stringed instruments were all popular throughout history. When Shakespeare was alive, more than 400 years ago, these instruments had been refined and developed into the harp, the fiddle, the viol, the dulcimer, the psaltery (a cross between a harp and a guitar), and the lute.
Galileo, one of the most influential scientists of Shakespeare’s time, conducted investigations into the science of stringed instruments. We can construct a simple one-stringed instrument to investigate how stringed instruments produce sounds, and how the length and thickness of a string affects its sound.
Traditional blues musicians like Bo Diddley and Lonnie Pitchford have used this instrument to make an amazing variety of songs. We’ve selected this instrument to make because it is capable of making a wide variety of musical notes even though it has only one string.
What’s the Science?
Sounds are created when air molecules vibrate — or move back and forth very fast. But random vibrations don’t create pleasant sounds that we consider to be music. If you’ve ever heard a blender, a vacuum cleaner, or a lawn mower, you know that not all noises are fun to listen to.
To make musical sounds, we need vibrations to happen in a precise way. The frequency of the vibration needs to stay constant, in order to create a stable pitch. The frequency of the vibration also needs to be controlled by the person making the music.
When you pluck a string on a stringed instrument, you pull it out away from the body of the instrument, and then release it. Pluck the string on your diddley bow and watch what happens. See if you can draw what the string looks like when it’s vibrating.
Now, slide the tin can along the string and stop it, then pluck the string again. What do you notice about the way the string moves? How does it affect the sound?
Move the tin can to different points along the string and try plucking it again. Where do you hear the highest pitch? Where do you hear the lowest pitch?
A string that is fixed at both ends, like on a stringed instrument, creates nodes, or points where there is no vibration, at each end. Think of two people turning a jump rope. The rope is turning, similar to the vibrating string. The handles are not turning, but are held in place, similar to the nodes.
When a vibrating string is in motion, it moves in a pattern called a wavelength. The height of the wavelength and its frequency determine whether a pitch is low or high. When you experiment with placing the can at different points on your diddley-bow string, you can see how much the string can move and fast it can move, and can notice how this affects the pitch.
All the different ways that strings can vibrate, or modes, have different wavelengths and different frequencies. The mode with the lowest frequency is called f1, or the fundamental. All the modes and the sounds they produce are called the harmonics of the string.
You can conduct a scientific investigation about the relationship between the length and tension of a wire and the sound it produces.
Brainstorm: Experiment with lots of different types of wire, string, cans, jars, and lengths. If you use screws to secure the wire of the diddley bow you’ll easily be able to adjust the amount of tension on the wire by rotating the screw.
Does increasing the tension in the string increase or decrease the pitch?
The length of the string that is free to vibrate is important. When you stop a string against the fingerboard you shorten the effective length. Does this raise or lower the pitch?
An ideal instrument produces a stable frequency that can be easily controlled by the player. Is your diddley bow an ideal instrument?
Many stringed instruments have a hollow box, or resonator, that lies beneath the strings. Design a resonator for your diddley-bow. You can make one from a cereal box. Make sure that you make a hole on the flat plane near the string. How does adding the resonator change the sound of your diddley-bow?
Investigate some stringed instruments from Shakespeare’s time, by looking at pictures and listening to recordings. How do their sounds differ from your diddley-bow? Why do you think they sound different?
Listen to blues musicians like Bo Diddley, Lonnie Pitchford, and Jessie Mae Hemphill, and learn more about their experiences with making music. Blues music has a unique sound, based on the ratios between the musical frequencies.
Vibration: moving back and forth very quickly.
Sound wave: an invisible vibration in the air that you hear as sound.
Frequency: the number of sound waves that pass a specific point each second.
Pitch: how high or low a sound is, depending on its frequency.
Take a picture and share it with us, so we can see what you made! Have an adult send it to email@example.com or share it using the hashtag #ScienceWorksOnline
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