How Do You Store a Tune in Metal? Pins on a Cylinder

A steel comb is cut into teeth of graduated length, and because a shorter tooth vibrates faster, each tooth sounds a different pitch when plucked. A brass cylinder rotates beside the comb, driven by a spring through a gear train, and pins projecting from its surface catch each tooth in turn, bend it and release it. The position of a pin around the cylinder determines when the note sounds and its position along the cylinder determines which note. The music is therefore stored as the physical arrangement of those pins, which is the same principle as a punched roll or card and predates both by a long way.

Several refinements distinguish a good instrument from a toy:

• •Dampers of fine feather quill that silence a tooth just before it is replucked
• •A governor with an air brake that holds the cylinder at a steady speed
• •Tuned weights on the underside of the bass teeth, lowering their pitch
• •A comb cut from a single piece of steel rather than assembled
• •A cylinder that shifts sideways at the end of a turn to play a different tune
• •A resonant wooden case, since the comb alone is nearly inaudible

The mechanism was developed in Switzerland around 1796 by Antoine Favre, a watchmaker in Geneva, who replaced the tiny bells then used in musical watches and snuffboxes with a tuned steel comb, which was far smaller, far louder for its size and far cheaper to make. That change turned a curiosity into a product. The industry concentrated in the Swiss Jura, in towns whose watchmaking workforce already possessed exactly the necessary skills, and grew through the nineteenth century into a substantial export trade. Pinning a cylinder was a specialist job requiring the position of every pin to be marked and drilled to a fraction of a millimetre, and a single cylinder might carry many thousands.

The characteristic tone comes from the physics of a plucked bar clamped at one end, which produces a set of overtones quite unlike those of a string. A string vibrating produces overtones at whole number multiples of its fundamental, which the ear reads as a single clear pitch. A bar produces overtones at ratios that are not whole numbers, which gives the sound its bell-like quality and makes the pitch slightly ambiguous. Steel also rings for a long time with very little damping, which is why the mechanism needs dampers at all and why the untreated sound is a wash of overlapping notes. The result is instantly recognisable and is very difficult to imitate with any other instrument.

The cylinder mechanism was displaced within a few decades by a disc version, patented in Germany in 1885, which used interchangeable steel discs with projections stamped out of them, so an owner could buy new music rather than a whole new machine. That was a genuine commercial revolution and the disc machines dominated by the 1890s. Both were then destroyed by the gramophone, which recorded actual performances rather than arrangements and cost less, and the industry collapsed within about fifteen years. The mechanism survives as a novelty in jewellery boxes and greetings cards, made in enormous numbers and usually with eighteen teeth, and a small number of workshops still restore antique instruments.

A comb of graduated steel teeth is plucked by pins on a rotating cylinder, with the pin position around the cylinder setting the timing and the position along it setting the note. Dampers, a speed governor and tuned bass weights distinguish a serious instrument. A Geneva watchmaker replaced tiny bells with a steel comb around 1796, and interchangeable discs from 1885 displaced cylinders before the gramophone destroyed both.