Organ stop

An organ stop can mean either:

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• The control on an organ console that selects a particular sound.
• The mechanism, and in particular the organ pipes, used to produce a particular sound.
• The sound itself.

Stops have particular names according to the kind of pipes used to create the sound and the style of organ.

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Single-rank stops, the majority, are usually marked with an arabic numeral indicating the pitch; it originated as the length, in feet, of the rank's longest pipe. Registration usually begins with an 8' on the manual and a 16' on the pedal; the pedal thus normally sounds an octave lower than played, providing the "full-bodied" sound typical of the organ. Halving the number raises the pitch by an octave; in growing a registration it is usual to draw next the 4', 2', etc. on the manual and the 8', 4', etc. on the pedal. Numbers other than powers of 2 appear; these are called mutations. The 5 1/3', 2 2/3', 1 1/3' series sounds a G for a C; the rarer 3 1/5', 1 3/5', 4/5' sounds an E for a C.

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The most common multi-rank stops are mixtures, and are usually marked with a roman numeral indicating the number of ranks. Though it seems somehow wasteful to not provide the ranks separately, a mixture rank may break - drop an octave - as one goes up the scale to avoid shrillness, making it inappropriate for use apart. The name applied to the mixture usually codes for the particular chord provided, but octaves and fifths are most common; e.g. a Quint III might provide the 5th, 8ve, and 12th; an Acuta IV might have the 15th, 17th, 19th, and 23rd. Mixtures are usually used to boost harmonics, but some are appropriate as solo stops.

Related Topics:
Mixtures - Roman numeral - Harmonic

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The next most common multi-rank stops are voix célestes, two identical ranks except one is slightly out of tune. But celestes are often presented as pairs of stops, since they don't break like mixtures.

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Sometimes a single rank has multiple stops. In one form, a divided or half stop, only the higher or lower pipes are drawn on. In another form, borrowing or unification, each stop may draw the rank to a different keyboard or to one keyboard at different pitches.

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Flue stops, such as principals, flutes, and strings, are essentially end-blown whistles. Reed stops, such as trumpets or vox humanas consist of a metal reed vibrating in a full- or partial-length resonator. Short-length reed resonators of unusual shape are often called "vowel chambers."

Related Topics:
Principal - Flute - Trumpet - Vox humana

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Names of stops are somewhat organ builder specific - a stop with a same name can have slightly different timbres on different organs.

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Organ stop: Mechanics of the Organ Stops ►