Grades 3–5 · Machines
How can little metal pins remember a tune?
A music box can play a tune without a loudspeaker or a computer. Inside, a cylinder carries tiny metal pins. Beside it sits a steel comb with carefully tuned teeth. The cylinder’s turning brings each pin toward a particular tooth.
In the diagramA tune stored in little metal pinsCylinder pins pluck the teeth of a steel combPins lift and release teethOne imagined tune0 slow2 smiddle4 shigh6 sA spring drives rotation; a governor steadies the pace.
A pin bends that tooth slightly, then releases it. The tooth vibrates and produces a musical note. Different teeth are tuned to different pitches. A tooth’s shape and mass help set its pitch; the cylinder chooses which tooth is plucked and when.
A wound spring commonly drives the cylinder through gears. A speed-regulating mechanism called a governor helps keep the pace steady. The illustration imagines four pin events equally spaced around one turn. If the turn takes eight seconds, the events occur at zero, two, four and six seconds. A faster turn brings the same sequence sooner. It does not retune the comb teeth. The pin arrangement stores the order and timing of the melody.
About this explanation
Starting knowledge: Know a complete turn and equal quarters.
Sources
- REUGE — Mechanical music movement