How Does a Machine Play an Organ? Holes in a Roll of Card
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A folding book of punched card passing over a row of holes opens and closes pipe valves in sequence, playing arrangements far beyond what a person could manage. The instruments were street furniture across Europe for a century.
How the music is stored
The instrument reads a physical record of the music, most often a long strip of stiff card folded into a zigzag book, punched with slots. That book is drawn steadily over a bar containing a row of small openings, one per note, and where a slot passes, air reaches a mechanism that opens the corresponding pipe valve, so the pipe sounds for exactly as long as the slot is long. Everything is therefore encoded in the position and length of the holes, with the position across the width giving the pitch and the length giving the duration, which is a direct physical representation of a musical score.
What one contains
The machinery divides into a few systems:
- •A bellows supplying air, driven by a crank or a motor
- •A reservoir smoothing the supply so the pressure stays steady
- •Ranks of pipes of different types, giving different tone colours
- •The reading mechanism drawing the book and sensing the holes
- •Percussion including drums and cymbals, operated from their own holes
- •A decorated front concealing the mechanism and directing the sound
Why the arrangements sound the way they do
The music has a characteristic quality that follows from the medium rather than from taste. A machine can play faster and more accurately than a person and never tires, so arrangers wrote elaborate runs, rapid repeated notes and dense chords that no organist could manage, which is why the arrangements sound busy. The instrument has a fixed number of notes available, frequently far fewer than a keyboard, so arrangers transposed, omitted and rewrote melodies to fit, and a recognisable tune on one of these has usually been substantially altered. Volume cannot be varied by touch, so contrast comes from switching ranks of pipes in and out, which is why the texture changes abruptly rather than gradually.
The machines it belongs with
Automatic musical instruments form a family and the differences are mostly in how the music is stored and what makes the sound. A music box plucks tuned steel teeth with pins set into a rotating cylinder or disc, which stores a short fixed piece. A player piano operates hammers from a roll of perforated paper, using suction rather than pressure, and reproducing versions recorded the playing of named pianists including dynamics. An orchestrion combines pipes, percussion and strings in one cabinet to imitate a small band. A carillon can be driven by a rotating drum with pegs that pull the bell hammers. What they share is a physical program that is read mechanically, which is a genuine ancestor of the punched card computing that followed.
Who owned them and what happened
These instruments were commercial equipment rather than domestic objects. Large ones were hired out by firms to operators who worked a territory, taking a share of the coins collected, and the books of music were rented and exchanged so that a repertoire stayed current with popular songs. Fairgrounds used enormous versions with dozens of ranks and figures that moved. Dance halls in the Low Countries used them instead of bands. Recorded music and amplification destroyed the business from the 1930s onwards, since a gramophone cost a fraction as much and needed no operator. Surviving instruments are maintained by collectors and municipal collections, principally in the Netherlands, Belgium and Germany, where they still appear on streets at weekends.
The takeaway
A folded book of punched card drawn over a row of openings lets air reach a valve wherever a slot passes, so pitch is encoded across the width and duration along the length. Arrangements sound busy because a machine can play what no organist could, and melodies are rewritten to fit a limited set of notes. The instruments were hired out commercially with rented music books until recording destroyed the trade.