Organ in Einsieldeln, Switzerland

The Organ

The traditional pipe organ is a collection of tuned pipes which are sounded by admitting air to them from a windchest. The centuries of development of the pipe organ have yielded a rich variation in types of pipes as well as mechanisms for sounding them. The collection of pipes of a given type is called a rank, and the organist's control knob for a rank is called a "stop". "Pulling the stop" means opening the valve to let air into that rank of pipes (when the corresponding key on the keyboard is pressed). Some of the largest organs have more than a hundred ranks.

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Types of Organ Pipes

The type of organ pipe that first comes to mind is that which has an edge with a slit called a flue which directs air from the windchest upon it. These are called flue pipes. Many varieties of pipes have been tried, and reed pipes are also popular.

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Ranks of Organ Pipes

A complete set of organ pipes of the same type is called a rank. In a large modern organ, the keyboard span is typically five octaves from C2 to C7. With 12 semitones per octave, this gives 61 pipes for a rank. Five doublings of length means that the longest pipe in a rank is 32 times the length of the shortest pipe.

Since the idea of a rank is to produce a set of pipes with similar tone quality, it has been found to be necessary to scale the diameters in a different way than the lengths. In order to enhance the higher harmonic content of the longer pipes, it has been found desirable to make their diameters smaller in proportion to their lengths. In a rank, the diameter of the longest pipe will be 12 to 13 times the diameter of the shortest pipe, while the length has increased by a factor of 32.

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