Music Box Cylinder

This simulation opens up a music box. A rotating drum carries pins that pluck the teeth of a steel comb, and each tooth rings at its own pitch. Students click the dots on the drum to add or remove pins, drag the drum with the pointer to turn it by hand, or let it turn on its own at a speed they choose. The right arrow key nudges it forward. Presets load a Twinkle melody, a rising scale or a zig-zag pattern, and readouts show the last note, its frequency, the tooth length and the number of pins. It shows that position around the drum is time, position along it is pitch, and shorter teeth sound higher.

• Choose the Empty pattern, then click dots on the drum to add pins and compose a tune.
• Drag the drum by hand to play the notes slowly, forward only, and watch the comb teeth wobble.
• Raise Turning speed and listen to the same pins play a faster tune.
• Compare the longest and shortest teeth using the Tooth length and Frequency readouts.
• Load Rising scale and then press Clear all pins to start again.

1. 1Explain how a pin on a drum represents time and pitch in a tune.
2. 2Describe why shorter steel teeth produce higher notes.
3. 3Predict how changing the turning speed affects the tempo of a melody.
4. 4Relate the length of a vibrating tooth to its frequency.

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