Organ stop

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The choir division of the organ at St. Raphael's Cathedral, Dubuque, Iowa. Shown here are several ranks of pipes, each of which would be controlled from one of the stops on the console. StRaphaelsDubOrganSmall.jpg
The choir division of the organ at St. Raphael's Cathedral, Dubuque, Iowa. Shown here are several ranks of pipes, each of which would be controlled from one of the stops on the console.

An organ stop is a component of a pipe organ that admits pressurized air (known as wind) to a set of organ pipes. Its name comes from the fact that stops can be used selectively by the organist; each can be "on" (admitting the passage of air to certain pipes), or "off" (stopping the passage of air to certain pipes).


The term can also refer to the control that operates this mechanism, commonly called a stop tab, stop knob, or drawknob. On electric or electronic organs that imitate a pipe organ, the same terms are often used, with the exception of the Hammond organ and clonewheel organs, which use the term "drawbar".

The term is also sometimes used as a synonym for register, referring to rank(s) of pipes controlled by a single stop. Registration is the art of combining stops to produce a certain sound. The phrase "pull out all the stops" has entered general usage, for deploying all available means to pursue a goal.


Organ pipes are physically organized within the organ into sets according to note and timbre. A set of pipes producing the same timbre for each note is called a rank, while each key on a pipe organ controls a note which may be sounded by different ranks of pipes, alone or in combination. The use of stops enables the organist to selectively turn off ("stop") certain ranks in order to produce different combinations of sounds, as opposed to hearing all sounds simultaneously. A stop may be linked to a single or multiple ranks. While nowadays one speaks of "drawing" a stop to select a particular rank or set of ranks, the earliest organs were constructed with all ranks "on" by default.

The mechanism for operating the stops varies widely, but the principle is the same: the stop control at the console allows the organist to select which ranks of pipes will sound when a key is pressed. When the organist desires a rank to sound, they operate the corresponding control at the console, allowing wind to flow to the pipes. Likewise, the organist can deny wind to the pipes by operating the same control in the opposite direction. Common stop controls include stop knobs, which move in and out of the console, and stop tabs, which toggle back and forth in position.

Some organs, particularly smaller historical organs from England, Spain or Portugal, [1] feature divided registers, in which there are two stop knobs for certain ranks. One stop knob will control the upper portion of the keyboard, and the other will control the lower portion of the keyboard. This arrangement allows the upper portion of the keyboard to sound a different registration than the lower portion, which lends a greater versatility to smaller organs, especially those with only one manual.

Ranks which are neither divided nor extended (see below Unification, borrowing and extension) generally contain as many pipes as there are keys on the keyboard to which they are assigned: in most cases 61 pipes for a rank assigned to a manual and 32 pipes for a rank assigned to the pedal.

Methods of actuation

Over the course of the history of the pipe organ, there have been several different designs by which stops are actuated. In the longest-standing design, known as the slider chest , there is a strip of material (typically wood) called a slider which fits underneath a given rank of pipes. The slider has small holes drilled in it, one for each pipe in the rank. When the stop is set such that pipes are inactive, the holes are misaligned with the pipes, preventing the air from flowing up into the pipes above. When the stop is set such that the pipes are active, the slider moves over, aligning the holes with the pipes, allowing air to reach them. Because the slider chest was developed before the advent of electricity, it is inherently mechanical in nature. Many organs originally built with mechanical actuators have been retrofitted with electric actuators.

Other common designs include the spring chest, the cone valve chest, and the Pitman chest.

Unification, borrowing and extension

The term unification refers to the practice of expanding the tonal resources of an organ without adding more pipes by allowing several different stops to control the same rank of pipes. For example, an 8′ Gedeckt may also be made available as a 4′ Gedeckt, either on the same or a different manual. When both of these stops are selected and a key (for example, C3) is pressed, two pipes of the same rank will sound: the pipe normally corresponding to the key played (C3), and the pipe one octave above that (C4).

Borrowing or duplexing refers to one rank being made available from multiple stop knobs, often on different manuals or pedal. [2] Extension refers to the addition of extra pipes to the high and/or low ends of a rank in order to allow that rank to be borrowed by higher and/or lower stops. Unification and borrowing (duplexing) is mostly related to pipe organs with physical pipes; however, some (older) electronic organs also used unification and duplexing to expand the tonal resources of a limited number of synthesized virtual ranks.

While unification and extension increase the tonal resources and flexibility of the organ, greater care needs to be taken by the organist in registering the organ, particularly when the composition requires many notes to sound at the same time. In a non-unified organ, voices are scaled for their intended job. As an example, the octave (4′) diapason is generally of a smaller scale and softer than the corresponding 8′ diapason rank, whereas in unification they would be of the same strength due to using the same set of pipes. Straight reed choruses (16′, 8′ and 4′) have the luxury of ranks with different timbres, whereas a unified reed chorus has voices that are identical.

Playing with all stops out on a heavily unified/duplexed organ may result in chords that sound thinner or emphasize higher harmonics on some notes more than others, due to notes in different octaves using the same pipes instead of having their own. Part of an organist's training is to detect unification and duplexing and to create registrations that take them into account. [3] Nonetheless, heavy unification can create issues for visiting artists with limited practice times, or those improvising compositions.

Borrowing between manuals occurs in English organs from about 1700,[ citation needed ] but extension of pipe ranks for the purpose of borrowing at different pitches is a relatively recent development.[ citation needed ] Extension and unification are heavily used in theatre organs to produce the maximum number of voices from a minimal number of pipes. It is still typical to see a significant amount of unification and duplexing in practice organs and small church organs. Traditionally, less use has been made of extension in large church organs and those designed for classical music, with authorities tending to regard borrowing in general and extension in particular as things to be avoided if possible, except in a few cases where space for pipes is limited, making extension and/or unification necessary. [4] [ citation needed ] Borrowing 16' manual ranks for the pedal division is more widely employed because of the expense and space requirements of 16' stops and the versatility this allows.

Pitch and length

The organ at the Naval Academy Chapel has 522 stops. Usnaconsole2.jpg
The organ at the Naval Academy Chapel has 522 stops.

The pitch produced by an organ pipe is a function of its length. All else equal, longer pipes produce lower-pitched notes, and shorter pipes are higher in pitch. An organ stop utilizes a set (rank) of pipes of graduated lengths to produce the range of notes needed. Stops with pipes tuned to sound the pitch normally associated with the keys (i.e. the pitch of the same keys on a piano) are called "unison stops". Other stops use pipework that is longer or shorter than that of unison ranks to speak at a fixed interval above or below unison pitch ("octave pitch" or "mutation pitch").

The pitch of a rank of pipes is denoted by a number on the stop knob. A stop which speaks at unison pitch, or "native pitch", is known as an 8′ (pronounced "eight-foot") stop. This nomenclature refers to the approximate length of the longest pipe in a rank of open pipes. In a rank of stopped pipes, the lowest pipe is about 4 feet long, but because it sounds at unison pitch, it is also known as an 8′ stop.


The octave sounded by a given pipe is inversely proportional to its length ("half the length = double the pitch"), meaning that a 4′ stop speaks exactly one octave higher than an 8′ stop. Likewise, a 2′ stop speaks one octave higher than a 4′ stop. Conversely, a 16′ stop speaks one octave below an 8' stop; and a 32′ stop speaks one octave below a 16′ stop. Octave pitch lengths used in actual organs include 64′, 32′, 16′, 8′, 4′, 2′, 1′, 12′, and 14′.


Organ keyboard unision pitch layout.png

Mutations and resultants

Ranks that do not speak at the unison or some octave of the unison pitch are called mutation stops, or sometimes "aliquots". They are rarely used on their own; rather, they are combined with unison stops to create different tone colors. A typical and distinctive sound of the organ is the cornet, composed of a flute and ranks making up its first four overtones, sounding 8′, 4′, 2+23′ (labeled 3′ on some German and Swedish organs), 2′, and 1+35′ (or 1+12′ on some German organs).

The sounding length of a mutation stop gives the answer as to what pitch the rank sounds. For example, a stop labeled 2+23′ (or one-third of 8′) has three times the frequency; i.e., the interval of a twelfth above unison pitch. This third harmonic (G) (twelfth, quint, qvinta, rorkvint, or nazard [nasard]) is the most-common pitch, followed by the fifth harmonic (E) (tierce [terz or ters on some organs]) (1+35′) and sixth (G) (larigot, nasat) (1+13′), with rarer examples from higher in the series, such as the "septième" or "septima" (1+17′) and "none" (89′). There's also an 8/15' Major 7th which when C4 is played it's sounding a B7 below the Top C8 of a Piano.

Mutations usually sound at pitches in the harmonic series of the fundamental, and except when derived from unified ranks, are always tuned pure. Some organs contain mutations that are overtones of 16' or 32' to create difference tones, e.g., quint-bass 10+23′. Such "helper ranks" that sound at the fifth just above or fourth below the fundamental (e.g., Bourdon 16′), can create the impression of a stop an octave lower than the fundamental (e.g., Bourdon 32′), saving the space and money otherwise needed for larger bass pipes; such an effect is termed a resultant.

This is a list of some mutation stops.

of pipe
Sounding note
when C4 is played
Name on manual
(1+12) [note 1] P55+13G4Quint
(2+12) [note 2] M103+15E5Gross Tierce
3P122+23G5Nazard, Twelfth
5M171+35E6Tierce, Terz
  1. 3rd harmonic of the note one octave below the fundamental
  2. 5th harmonic of the note one octave below the fundamental


Certain stops called mixtures contain multiple ranks of pipes above unison pitch, usually octave and fifths. The number of ranks in a mixture is denoted by a Roman numeral on the stop knob; for example, a stop labeled "Mixture V" would contain five pipes for every note. So, for every key pressed, five different pipes sound (all controlled by the same stop). A mixture made of octaves and fifths is called a 'quint mixture', while a mixture made of octaves, fifths, and a major third is called a 'tierce mixture'. As a rule, the fifths and thirds of mixtures are tuned pure in relation to the fundamental. For thirds, the 14 cent discrepancy between the just and equal tempered interval is large enough to introduce noticeable beating in chords, and tierce mixtures became uncommon with the abandonment of meantone temperaments.

Mixtures have numbers that correspond to the pitch they make. For example, a mixture configured as: contains, at its lowest note, the following ranks: 2 2/3', 2', 1 1/3', 1'.

Mixtures usually have 'breaks' to prevent the inconvenience to the builder of making very small pipes at the top of the compass. A common configuration for the breaks is that for every octave the mixture lowers by a fifth.


A cornet organ stop is similar to that of a mixture, but they are primarily used as solo voices, though their sound is not imitative of the orchestral cornet. A cornet will always contain the fifth and major third, and, depending on the number of ranks, may contain octaves, and more rarely the minor seventh, and ninth. A cornet pipes are made of metal and voiced as flutes, the 8' rank is usually made of stopped metal pipes. The ranks will be justly tuned to reinforce the fundamental.

The most common configuration of ranks for an 8' fundamental is as follows: II = 12.17; III = 12.15.17; IV =; V =

Cornet stops do not usually play the full compass; they generally play from either Middle C, or Tenor C, to the top. In British and French organs before the Victorian period, this allowed the Cornet stop to be raised up within the case relative to the other pipes of the Great organ around it for better projection; this is known as a 'Mounted Cornet' in English and 'Cornet Séparée' in French. Though used throughout Europe, the Cornet is especially associated with French organ builders, who used Cornets with particular regularity especially through the Eighteenth and Nineteenth centuries, since French chorus reed stops (Trompette, Bombarde, Clairon) are very strong in the bass (having un-weighted tongues) but, when on low wind pressures, comparatively weak further up the compass; the Cornet was therefore used to strengthen the treble ranges of these chorus reed stops. A characteristic example of this use is the classic French registration known as the 'Grand Jeu': a combination of Trompettes, Clairons and Cornets, together with the Prestant (by contrast the 'Plein Jeu' does not include cornets).

In French organs, when an 8 ft Bourdon was used with 4' and 2' stops plus a Nasard and Tierce the resulting ensemble was known as a 'Cornet Décomposée' (often confused with the 'Cornet Séparée' described above) since it had the same composition as a standalone Cornet stop.

Occasionally Cornets are supplied based on a 16' fundamental (16', 8', 5 1/3', 4' and 3 1/5'), though the individual ranks are more usually configured as separate stops (for example the Grande Tierce 3 1/5' and Grand Nasard 5 1/3' supplied by the Isnard brothers at St Maximin, Provence). 32-ft based cornets are also known, as they are able to approximate the sound of a 32' reed stop without the using pipes of the same bulk or expense (as used for example by John Compton at Wakefield Cathedral, England).


A Sesquialtera (or Sexquialtera) is similar to a Cornet in that it always contains a fifth and major third (justly tuned), though they normally extend to the whole range of the compass. They also rarely go beyond IV ranks, the most common being found at II or III ranks. They are not necessarily as uniform in configuration as the Cornet and so the quint and tierce ranks can be placed anywhere in the configuration. For example, the configurations: 15.17.19, 17.19.22, and 19.22.24 are all equally valid as the configurations for a Sesquialtera.

Sesquialtera stops can be solo or chorus stops. The British Victorian Sesquialtera was often the only Mixture stop on a given department (usually the Great or Swell organ; rarely the Choir organ), typically starting at 17.19.22 and then breaking back to 12.15.17 further up the compass and intended to be used in the chorus to help blend reed and flue stops together. By contrast, the Dutch, German and Scandinavian Sesquialteras of the seventeenth and eighteenth century were solo stops (typically 12.17), often (though by no means exclusively) found in the Rückpositiv division, from whose gallery-edge case position they could project a solo line well into acoustic space against an accompaniment using stops in the main organ case; such Sesquialteras are therefore particularly associated with Lutheran chorale-based organ repertoire.

Sesquialteras are often distinguished from Cornet stops because whereas Cornets (especially French examples) use wide-scaled, flute-toned pipes, Sesquialteras were generally made from narrower, principal-toned pipes (though this distinction is somewhat less widely observed in 20th-century organs than earlier organs). Sesquialteras therefore often have a sharper sound than Cornets.


Pipe ranks have particular names, which depend on a number of factors ranging from the physical and tone attributes of the pipes in that rank, to the country and era in which the organ was manufactured, to the pipes' physical location within the organ. Each stop knob is labeled with the name of the rank it controls. In general, that label gives the organist two vital pieces of information about the rank of pipes in question:

This is an example of a pipe organ stoplist, showing both common stop names and conventional formatting. Within each division, flues are listed before reeds, then low to high pitch, then louder to softer stops within a pitch level. Separate celeste stops are next to their corresponding normally-tuned stops. Reed stops are often labeled in red on stop knobs or tabs.

Classifications of stops

Organ pipes fall into five broad categories:

Percussion stops (often referred to as "toy counters" or "toy stops"), unlike other organ stops, are not aerophones, but actual embedded percussion instruments (although they may still be actuated by the wind supplies of an organ). Both tuned and untuned percussion stops exist (for instance, marimba and snare drum, respectively). They are commonly designed to imitate orchestral or band instruments, or to imitate non-musical sounds (for instance, thunder), or to produce unique sounds (for instance, zimbelstern). Percussion stops are particularly common in theatre organs, which were generally made to accompany silent films.

Notable examples

Related Research Articles

Pipe organ Wind instrument controlled by keyboard

The pipe organ is a musical instrument that produces sound by driving pressurized air through the organ pipes selected from a keyboard. Because each pipe produces a single pitch, the pipes are provided in sets called ranks, each of which has a common timbre and volume throughout the keyboard compass. Most organs have many ranks of pipes of differing timbre, pitch, and volume that the player can employ singly or in combination through the use of controls called stops.

Overblowing is a technique used while playing a wind instrument that causes the sounded pitch to jump to a higher one primarily through the manipulation of the supplied air rather than by a fingering change or the operation of a slide. Depending on the instrument, and to a lesser extent the player, overblowing may involve a change in the air pressure, in the point at which the air is directed, or in the resonance characteristics of the chamber formed by the mouth and throat of the player. In some instruments, overblowing may also involve the direct manipulation of the vibrating reed(s), and/or the pushing of a register key while otherwise leaving fingering unaltered. With the exception of harmonica overblowing, the pitch jump is from one vibratory mode of the reed or air column, e.g., its fundamental, to an overtone. Overblowing can be done deliberately in order to get a higher pitch, or inadvertently, resulting in the production of a note other than that intended.

A mixture is an organ stop, usually of principal tone quality, that contains multiple ranks of pipes including at least one mutation stop. It is designed to be drawn with a combination of stops that forms a complete chorus. The mixture sounds the upper harmonics of each note of the keyboard, adding a chord to each note played. The individual pitches in the mixture are not distinguished by the listener; rather, they reinforce the fundamental pitches of the chorus, adding volume and brilliance to the sound. Because pipes playing upper harmonics produce their own set of harmonic overtones, an element of harmonic dissonance is introduced, giving mixtures their characteristic tonal texture as they enrich the ensemble. Historically, the mixture descends from the medieval Blockwerk concept, an organ in which there were no stops and all the ranks sounded simultaneously.

Organ flue pipe scaling

Scaling is the ratio of an organ pipe's diameter to its length. The scaling of a pipe is a major influence on its timbre. Reed pipes are scaled according to different formulas than for flue pipes. In general, the larger the diameter of a given pipe at a given pitch, the fuller and more fundamental the sound becomes.

Pedal keyboard Musical keyboard played with the feet, usually used for low-pitched notes

A pedalboard is a keyboard played with the feet that is usually used to produce the low-pitched bass line of a piece of music. A pedalboard has long, narrow lever-style keys laid out in the same semitone scalar pattern as a manual keyboard, with longer keys for C, D, E, F, G, A and B, and shorter, raised keys for C, D, F, G and A. Training in pedal technique is part of standard organ pedagogy in church music and art music.

Theatre organ Type of pipe organ

A theatre organ is a distinct type of pipe organ originally developed to provide music and sound effects to accompany silent films during the first 3 decades of the 20th century.

Flue pipe

A flue pipe is an organ pipe that produces sound through the vibration of air molecules, in the same manner as a recorder or a whistle. Air under pressure is driven through a flue and against a sharp lip called a labium, causing the column of air in the pipe to resonate at a frequency determined by the pipe length. Thus, there are no moving parts in a flue pipe. This is in contrast to reed pipes, whose sound is driven by beating reeds, as in a clarinet. Flue pipes are common components of pipe organs.

Organ pipe Musical instrument part

An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air is driven through it. Each pipe is tuned to a specific note of the musical scale. A set of organ pipes of similar timbre comprising the complete scale is known as a rank; one or more ranks constitutes a stop.

Bourdon, bordun, or bordone normally denotes a stopped flute/flue type of pipe in an organ characterized by a dark tone, strong in fundamental, with a quint transient but relatively little overtone development. It is half-length construction makes it especially well suited to low pitches, economical as well, and the name is derived from the French word for 'bumblebee' or 'buzz'.

Chorus is an audio effect that occurs when individual sounds with approximately the same time, and very similar pitches, converge and are perceived as one. While similar sounds coming from multiple sources can occur naturally, as in the case of a choir or string orchestra, it can also be simulated using an electronic effects unit or signal processing device.

Gedackt is the name of a family of stops in pipe organ building. They are one of the most common types of organ flue pipe. The name stems from the Middle High German word gedact, meaning "capped" or "covered".

St Mary Moorfields Church in City of London, England

St Mary Moorfields is a Roman Catholic church in Eldon Street near Moorgate, on a site previously known as Moorfields. It is the only Catholic church in the City of London. Prior to 1994, the church was designated as being in the Borough of Hackney, such that there were no Catholic churches in the City.

This article describes the process and techniques involved in the tuning of a pipe organ. Electronic organs typically do not require tuning.

A Tibia Clausa is a type of pipe organ pipe. It is a large-scale, stopped wood flute pipe, usually with a leathered lip. The rank was invented by Robert Hope-Jones. Tibia Clausas provides the basic foundation tone of the organ with few overtones or harmonics. The Tibia Clausa is arguably the most important rank of pipes in a theatre pipe organ, with some organs having as many as 5. The stop shares similarities with the Bourdon and the Gedackt found in some church pipe organs. In the 18th and 19th centuries, Tibia Clausa was sometimes used as an alternate name for Doppelflöte. Most tibias are made from wood, as by Wurlitzer etc., although examples of metal tibias may be found made by the John Compton Organ Company.

Organ console

The pipe organ is played from an area called the console or keydesk, which holds the manuals (keyboards), pedals, and stop controls. In electric-action organs, the console is often movable. This allows for greater flexibility in placement of the console for various activities. Some very large organs, such as the van den Heuvel organ at the Church of St. Eustache in Paris, have more than one console, enabling the organ to be played from several locations depending on the nature of the performance.

Registration is the technique of choosing and combining the stops of a pipe organ in order to produce a particular sound. Registration can also refer to a particular combination of stops, which may be recalled through combination action. The registration chosen for a particular piece will be determined by a number of factors, including the composer's indications, the time and place in which the piece was composed, the organ the piece is played upon, and the acoustic environment within which the organ resides.

Accordion reed ranks and switches

A reed rank inside an accordion is a single full set of the reeds that are the means to achieve the instrument's sound range. These reed ranks are located in the reed chamber. Most accordions to this date typically have between two and four reed ranks on the treble side and between three and five reed ranks on the bass side. These can usually be selected individually or combined in various ways to provide a range of different timbres, by use of register switches arranged by register from high to low. More of the top-line expensive accordions may contain five or six reed blocks on the treble side for different tunings, typically found in accordions that stress musette sounds.

A cornet, or Jeu de Tierce, is a compound organ stop, containing multiple ranks of pipes. The individual ranks are, properly, of flute tone quality but can also be of principal tone. In combination, the ranks create a bright, piquant tone thought by some listeners to resemble the Renaissance brass instrument, the cornett.

On classical French organs, the plein jeu is a principal-based plenum registration. It includes the Montres, Bourdons, Prestants and Doublettes and the Fournitures and Cymbales. The classical French organ also allows for a reed-based registration; the grand jeu, which used a loud combination of reed stops in homophonic sections of larger pieces or standalone préludes.

St Peter and St Paul, Bromley Church in Kent , United Kingdom

St Peter and St Paul is a church in the town of Bromley, Borough of Bromley, in south east London. Known familiarly as Bromley Parish Church, it is not far from Bromley High Street and approximately halfway between Bromley North and Bromley South railway stations. The church is part of the Diocese of Rochester within the Church of England. Largely destroyed by bombing during the Second World War, St Peter and St Paul was rebuilt in the 1950s. It has been Grade II* listed since 1955.


  1. James Dalton, "Iberian organ music before 1700," in The Cambridge Companion to the Organ , ed. Nicholas Thistlethwaite and Geoffrey Webber (Cambridge University Press, 1998), p. 165.
  2. John R. Shannon, Understanding the Pipe Organ, 2009, p. 83.
  3. John R. Shannon, Understanding the Pipe Organ, 2009, Chapter 6.
  4. Audsley, George Ashdown (1905). The Art of Organ-Building. New York: Dodd, Mead, and Company. p. 13.
  5. Grenzing, Gerhard (1993). "Jordi Bosch—The Unknown Master" (PDF). ISO Yearbook: 114–116, 143.
  6. Frankel, Stuart. "Notes about Historical Registration on the Santanyí Organ". Sonus Paradisi.

Further reading