HOW DOES AN ORGAN WORK?

Franz Liszt used to say that it was the king of instruments. It is true that its size, the sumptuousness of its case, the richness and diversity of the sounds produced by its "stops", its power, confer on it a special rank in the instrumental concert.
Belonging to the wind-instrument family, it is equipped with a multitude of pipes, each dedicated to a single note. These pipes are of two types according to the means of sound production.
The labial pipes, that constitute what the organists call foundation stops, work like a recorder. Of various tones according to their diapason (the ratio between the length and the diameter of the body), they give to the organ the richness and depth of sound, but also the clarity and the shimmering for the high-pitched stops.
In the reed pipes, the sound generating system is made of a brass tongue that vibrates on a brass shallot when the air is forced through. Of equally varied tones according to the diapason and the shape of the resonator (conical, cylindrical, cylindro-conical, etc.), the reeds bring to the organ the straight colours of solo stops (Cromorne, Clarinet, Oboe, Vox humana) and the outstanding power of the great reed choruses (Bombarde, Trompette, Clairon).
For all the pipes, the length of the body determines the height of the sound: the longer the pipe, the lower the sound.

One can only see a small part of the pipework of an organ. The exposed pipes are actually most often less than 2% of the total. They have a double function since they play an important part in the case's general aesthetic quality. As they are exposed (hence the word Montre in French, which means "to show", and designates the 8’ Principal), they are made and polished with extra care. The stops made up of other pipes are most often named after the instruments that inspired their tone, and are arranged in different parts of the case.

The specification of each instrument is unique; every era, every country has its own style of organ. The stoplist of an organ and the way it is divided between the manuals determine a style and, consequently, the repertoire that can be played on the instrument.

An organ comprises one or more manuals and most often a pedalboard, each controlling a division that occupies a distinct spatial position. The Gisors organ has three manuals and a pedalboard. The first manual controls the Positif which is the smaller organ case located in front of the big one. The second manual controls the Great Organ division situated in the large organ case. This division is the richest and also the most powerful except for the Pedal. The third manual controls the Brustwerk which is located under the Great organ, just above the console. It is composed of softer and solo stops. As for the Pedal, which comprises the lowest-pitched stops, it is usually situated in the side towers due to the length of the pipes (the lowest note of this organ is produced by a 16-foot pipe).

When the organist presses a key on a manual keyboard or on the pedalboard, for the concerned division, a pallet opens to let the air in a groove that feeds all the pipes that correspond with the same note. Only the stops pulled out by the organist will let the note speak.

The organist has therefore to choose the stops he wishes to use before playing by pulling stop knobs on each side of the manuals. Having several keyboards at his disposal allows him to easily use several combinations of sounds while playing without having to move his hands away from the keyboards to pull other stops. It also enables him to establish a dialogue between the different divisions of the organ. To make the sound louder, all you need is to add more stops, or to couple the manuals together by means of combination pedals that add divisions to each other. Coupled manuals then reproduce the notes that are played on the manual they are coupled to and add their stops to the previous one. The organist must juggle with all these possibilities to turn into a conductor and become himself an entire orchestra for our ears’ greatest pleasure.

To learn more about the functioning of the organ and its history, one may consult the following books:

• DUFOURCQ, Norbert, L'orgue, Que sais-je n° 276, Paris : PUF, 1948, 130 p.
• ROCHAS, Pierre, COLIN, Michel, Le petit dictionnaire de l'orgue illustré, coll. Passerelles, Arles : Harmonia Mundi, 1997, 49 p. + 2 CD.
• CELLIER, Alexandre, Bachelin, Henri, L'ORGUE : ses éléments - son histoire - son esthétique, Marseille : Laffitte Reprints, 1980, 254 p. reprod. de l'éd. de Paris : librairie Delagrave, 1933.
• SONNAILLON, Bernard, L’ORGUE : instruments et musiciens, Paris : Office du Livre, Éditions Vilo, 1984, 258 p.
• THOMANN, Marcel, Le Monde Mystérieux de l’Orgue, Strasbourg : Éditions du Signe, 1998, 96 p.
• TEULON, Bernard, de l’orgue, Aix-en-Provence : Éditions Édisud, 1981, 196 p.
• SUMNER, William Leslie, The Organ: its evolution, principles of construction and use, London: Macdonald & Co., 1962, 544 p., 3rd edition of the original published in 1952.
• BARNES, William Harrison, The Contemporary American Organ: its evolution, design and construction, Glen Rock, New Jersey: J. Fischer & Bro., 1964, 389 p., 8th edition of the original published in 1930.

The organ enthusiasts will dive with delight into the Talbott Library catalog that the Organ Historical Society (http://www.organsociety.org/) puts on line and which is certainly the most complete data available today on the subject (40 000 items).

 

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