How does a pipe organ work?
Behind the immense pipes of the Great Organ of Beauvais Cathedral lies a remarkable musical machine. Wind, pipes, windchests, keyboards and stops all work together, allowing a single musician to command thousands of voices.
Thousands of pipes controlled by a single musician
When looking at the Great Organ of Beauvais Cathedral, the enormous metal pipes of the façade are the first things to catch the eye. Yet most of the instrument remains hidden from view.
Behind the organ case are thousands of pipes, wind reservoirs, windchests, ducts and an entire transmission system allowing the organist to choose which sounds will be heard.
The organ is therefore at once a wind instrument, a keyboard instrument and an extraordinary machine.
Wind
A blower produces and maintains air under pressure.
A command
The organist selects a stop and presses a key or a pedal.
A sound
The wind reaches the corresponding pipes, which then produce their sound.
It all begins with air
Without air, an organ remains silent. Its fundamental principle is to send pressurised air — traditionally called wind — into the pipes selected by the organist.
In the past, assistants known as bellows blowers manually operated large bellows. Today, an electric blower supplies the necessary wind. It is stored and regulated before being carried to the windchests.
The wind is therefore permanently available. But for a pipe to speak, the organist must still open the correct path leading to it.
Why does an organ need thousands of pipes?
Each pipe is designed to produce a particular pitch and tone colour. Generally speaking, the longer the pipe, the lower the note it produces.
The largest façade pipes of the Beauvais organ reach 11.70 metres in length, while some of the high-pitched pipes hidden inside the instrument are extremely small.
Flue pipes
They work according to a principle similar to that of a flute. Wind enters through the foot of the pipe and passes the opening known as the mouth.
The air column inside the pipe begins to vibrate, producing the sound.
Examples: Principal, Bourdon, Flute, Gamba…Reed pipes
In these stops, the wind causes a small metal tongue — the reed — to vibrate.
A resonator then amplifies and colours this vibration.
Examples: Trumpet, Clarion, Oboe…What is an organ stop?
A stop is a rank or set of pipes sharing the same tonal identity.
It can be imagined, in simplified terms, as a huge pan flute: each pipe produces a different note, but all the pipes in the rank belong to the same family of sound.
With its 77 stops, the Beauvais organ therefore possesses an exceptionally broad tonal palette.
Some families of sound
Principals
The traditional tonal foundation of the organ.
Flutes and Bourdons
Rounded, gentle or bright sounds.
Strings
Slender tones recalling bowed string instruments.
Reeds
Trumpets, clarions and oboes provide brilliance,
power and character.
How does the windchest send air to the right pipe?
The windchest is the organ’s main distribution centre. Pressurised wind is constantly available beneath the pipes, but it can only reach them when the organist combines two actions: selecting a stop and playing a note.
The animation below is a deliberately simplified representation of a windchest. First select the stop, then press the key: you will see the pallet open and the wind reach the pipe.
Build your own sound
This simplified console demonstrates the principle of registration. Select one or more stops, then press a note.
Four manuals and a pedalboard
The organist of the Great Organ of Beauvais has four manual keyboards and a pedalboard.
Each manual controls a group of stops known as a division. The organist can therefore contrast different tone colours, make them answer one another or combine them.
What is the pedalboard for?
The large keyboard beneath the organist’s feet controls, among other things, some of the lowest sounds of the instrument.
The organist can therefore play a melody with the right hand, an accompaniment with the left hand and a third musical line with the feet.
Remarkable coordination
The hands may play on several manuals while the feet move across the pedalboard.
At the same time, the organist may need to change stops, operate couplers and use other controls at the console.
A single musician therefore controls an entire architecture of sound.
From the key to the pipe
The blower produces the wind
Air is placed under pressure.
The wind is regulated
Reservoirs maintain a steady supply of wind to the instrument.
The organist selects the stops
This determines which families of pipes are available to speak.
A note is played
A key on a manual or a pedal is pressed.
The windchest distributes the wind
Wind is directed only towards the corresponding pipes.
The pipes speak
The wind causes the pipes to produce sound, which spreads throughout the cathedral.
Registration: choosing the colours
Playing the organ involves much more than simply playing the notes written in a score.
The organist must also choose which stops to use. This selection and combination of stops is known as registration.
A few gentle stops can create an intimate atmosphere. Other combinations allow the different manuals to answer one another. Finally, gradually combining many stops can produce the monumental sound of the full organ.
In Beauvais, the organist does not simply play the organ: in a sense, the organist also plays with the cathedral’s extraordinary architecture.
The cathedral is part of the instrument
The Great Organ stands at the western end of the cathedral on its vast organ loft.
Sound produced by the pipes travels through the immense interior of Saint Peter’s Cathedral. The vaults, walls, nave and choir reflect and prolong the sound.
The organist must therefore take this reverberation into account. A registration or interpretation suited to a small building will not produce the same result in the immense space of Beauvais Cathedral.
The Great Organ of Beauvais Cathedral
Several organs have succeeded one another in Beauvais Cathedral since the 16th century.
The present Great Organ was built by Danion-Gonzalez and completed in 1979. It has 77 stops and approximately 5,500 pipes.
The key action is mechanical, while the stop action is electric. This combination of traditional craftsmanship and modern technology has created an instrument capable of performing an exceptionally broad repertoire.
From early music to the great symphonic and contemporary works, the richness of its tonal palette allows the instrument to enter into a remarkable dialogue with the monumental architecture of Saint Peter’s Cathedral.
Discover the history of the Great Organ
How an organ works is only one part of its story. Discover the instruments that have succeeded one another in Beauvais Cathedral since the 16th century and the creation of today’s monumental Great Organ.
The Great Organ of Beauvais Cathedral