Music Box Mechanism Simulator (2D)

Crank

Crank speed 40 RPM

Melody / pin pattern

Cylinder turning — pins lifting the comb teeth.

Live Readout

Current note

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Cylinder RPM

How it works

A music box cylinder is studded with small metal pins arranged around its surface. As a wound spring (or, here, a hand crank) turns the cylinder at a steady speed, each pin sweeps past and plucks one tine of a flat steel comb mounted alongside it, then releases it to spring back and ring — the same principle as plucking a tuned reed.

Every tooth on the comb is a tiny cantilever beam. Its natural frequency depends on its length: for a beam of uniform cross-section, resonant frequency scales roughly as 1/L², so a long tooth vibrates slowly (low pitch) and a short tooth vibrates fast (high pitch) — exactly like the bars of a xylophone or the tines of a kalimba, just plucked mechanically instead of by hand.

The tune itself lives entirely in geometry: which pin sits at which angular position around the cylinder, and how far along its length, fixes both when a note sounds (rotation angle → time, set by the crank speed) and which tooth it strikes (axial position → pitch). Changing the pattern below swaps which pins are punched into that cylinder, the way a music-box maker would design a new tune without changing the comb at all.