Make a string instrument
Build a simple string instrument using a cardboard box, rubber bands, and a straw bridge, then explore how string tension and length change pitch.
About this activity
Build a simple string instrument using a cardboard box, rubber bands, and a straw bridge, then explore how string tension and length change pitch.
What you need
Step by step
- 1
Step 1
Gather all the materials and bring them to a clear table or floor space.
- 2
Step 2
Put the box on the table with the open side facing up so the top is flat.
- 3
Step 3
With adult help use the scissors to cut two small matching slits on opposite sides of the box near one short end.
- 4
Step 4
Thread the straw through the slits so it sits across the top as a bridge and trim any extra straw if needed.
- 5
Step 5
Stretch 3 or 4 rubber bands lengthwise over the box so each band rests on top of the straw bridge.
- 6
Step 6
Move the rubber bands with your fingers so they are spaced evenly across the box top.
- 7
Step 7
Pluck one rubber band with your finger and listen carefully to the pitch it makes.
- 8
Step 8
Make that same band tighter by pulling its end and looping it once around the box edge to increase tension then pluck it again.
- 9
Step 9
Loosen that same band by undoing the loop so it is less tight then pluck it again.
- 10
Step 10
Slide the straw bridge closer to the middle of the band to shorten the vibrating length then pluck the band.
- 11
Step 11
Slide the straw bridge farther toward the end of the box to lengthen the vibrating length then pluck the band.
- 12
Step 12
Compare the sounds and say which change made the pitch higher or lower.
- 13
Step 13
Share your finished instrument and what you discovered about pitch on DIY.org.
Fun facts
How do you build a simple string instrument with a cardboard box?
To make a cardboard-box string instrument, stretch several rubber bands around the box’s width so they sit over the open side. Position a straw (cut lengthwise or whole) under the bands to act as a bridge; tape it down. Pluck each band and tighten by twisting or move where the band rests to change pitch. Experiment by shortening a band against the bridge or pressing to fret different notes. Supervise cuts and use blunt scissors for young children.
What materials do I need to make a simple string instrument?
You need a small cardboard box (shoe box works well), several rubber bands of different widths, a drinking straw or small wooden dowel for a bridge, tape, scissors (adult use), and a ruler. Optional: paper clips or clothespins for fastening and varying tension, markers to decorate, and a small notebook to record pitches. Avoid very small elastic bands for toddlers due to choking risk.
What ages is this string instrument activity suitable for?
This craft suits preschoolers (4–5) with close adult help, especially for cutting and handling small parts. Ages 6–9 can build with supervision and explore how length and tension affect pitch. Ages 10+ can design experiments measuring changes, compare tension quantitatively, and try multiple bridge types. Always supervise scissors and small parts for younger children to prevent choking or accidental injury.
What are the benefits, safety tips, and fun variations for the cardboard string instrument?
Making and playing the instrument teaches basic physics (pitch, tension, length), fine motor skills, creativity, and listening. Safety: supervise scissors, keep small elastics away from toddlers, and use tape to secure bridges. Variations: add more rubber-band “strings,” change bridge materials (eraser, pencil), use different box sizes, or measure and graph pitch changes. Turn it into a garage-band project by decorating and composing simple songs together.
Watch & Learn
Need help?
What can we use if we don't have a straw or the exact box called for in the instructions?
Use a pencil, chopstick, or wooden skewer threaded through the slits as the bridge and substitute a shoebox, cereal box, or other small cardboard box placed open side up for the instrument body.
The straw bridge keeps falling out or the bands make almost no sound—how can we fix that?
If the straw slips or wobble, make the two matching slits from step 3 smaller or tape the straw from step 4 in place and, if bands are quiet, tighten them by looping the end around the box edge as in step 7 or trim and retension them.
How can we adapt this activity for younger or older children?
For ages 3–5 have an adult pre-cut the slits and hold the box while the child stretches and plucks 1–2 rubber bands, for ages 6–9 let them thread the straw bridge and test tightening/loosening, and for 10+ challenge them to add more bands, measure pitch changes when sliding the straw per steps 11–12, and record observations.
What are simple ways to extend or personalize the string instrument activity?
Decorate the box with paint or stickers, try different widths or colors of rubber bands and add a second straw bridge to make chords, then compare how each change affects pitch and share your discoveries on DIY.org as the final step.