Page 156 - Chorister's Companion
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                                                                  The Organ
How do organs work?
The details are complicated, but the basic facts involve air and pipes. Nowadays the air is generated by an electric fan, but before the age of electricity the bellows had to be pumped manually. Often this job fell to the choristers, and if the organ was large it was very hard work.
All that air is stored in a box or reservoir and sent through the organ. When a key is pressed, various parts of the mechanism called the action (which might be direct and mechanical, or electric, or even pneumatic) open very small trap doors (called pallets) under the pipes and allow air into them.
Pipes produce all the different notes of the organ. The ones which you can see are almost certainly just a fraction of the total number of pipes. All of the remaining pipes are inside the instrument in what we call the case.
On an average-sized church instrument, there might be about 800 pipes. You can probably see only about 20 to 50 of those on the front and side of the organ!
The outside of the case might be very decorated and impressive. The insides, though, are often very complex, compact and sensitive (and sometimes dangerous, too). You should never go inside without adult supervision.

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