This basic glossary has been produced to help those interested in organs but unfamiliar with organ terminology.  If you have any queries about words that aren’t listed below, then please send us an email and we’ll add it to our list.  More detailed information can be found in various textbooks, such as Organ Works by John Norman (2020), obtainable from the British Institute of Organ Studies.

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ACTION: The organ’s mechanism; or, more specifically, the mechanism which links the keyboards to the organ pipes.  When a key is pressed, the ‘key action’ operates a set of valves, or Pallets, in the Windchest to admit wind into the pipes. The ‘stop action’ (or ‘drawstop action’) allows the organist, by drawing Stops, to control which ranks of pipes are engaged. 

The oldest form of action is Tracker (or Mechanical) action, with a direct mechanical connection between the keyboard and the pipes.  From the mid-nineteenth century onwards, as organs grew bigger and more complicated, various forms of power-assistance have been devised to lighten the touch at the keyboard: e.g. Pneumatic action,  Electro-pneumatic action.

Sloane Street, Holy Trinity - zinc basses(2)BASSES: The largest pipes in the organ.  The bottom notes of a given stop.
Detall_orgue_7BELLOWS: The traditional apparatus used for blowing organs (by hand or foot) until the introduction of the electric fan in the latter part of the nineteenth century. The picture shows a ‘wedge bellows’, used from medieval times. See also Blower, Reservoir.
BLOWER: For centuries organs were blown by hand or foot, but mechanical blowing began to be introduced from the mid-nineteenth century (at first using steam, gas or water power), and now electric rotary fans are almost universal. The wind passes from the blower to one or more Reservoirs, which supply a constant pressure to the wind chests
BODY: The upper part of a flue pipe, measured upward from the mouth to the end of the pipe. A pipe body may be either open, closed or partially closed.
BOOT: The lower part of a reed pipe, containing the sound-producing mechanism: shallot and tongue.
BUILDING FRAME: The structure upon which the organ components are set. Usually constructed of wood, jointed and bolted together.
CASE: The wooden enclosure for the organ pipes and mechanism.  An important visual and acoustic element of many organs; may be handsomely decorated.
Edington Priory - Vox Celeste pipe bodyCELESTE: A rank of pipes similar in scale and voicing to another rank on the same chest, intentionally tuned either sharp or flat in comparison to the unison rank. The effect when the two ranks are played together is a gentle undulation in the pitch.
CHEST: See Windchest
ChoirCHOIR ORGAN:  The third division of a three-manual organ, normally played from the lowest keyboard (the other two keyboards controlling the Great and Swell Organs). The name is a  corruption of the old term ‘Chair organ’, which referred to a division placed behind the organist’s bench (like the German ‘Rückpositiv’).  Later it came to refer to a division within the main part of the organ, with the possible implication that it may be used for accompanying a choir of voices.
 COMPASS: The range of a keyboard, referring to the normal pitch of the keys themselves, not of the actual sounding pitch of a specific stop. Thus, in normal usage, “compass” refers to the keys, “range” to the pitches played by those keys.
CONSOLE: The console consists of a cabinet containing the manual and pedal keyboards and the stop control. The console is either built into the organ case or detached from it and there is a bench for the organist to sit. Parts of the organ action are found in the cabinet.
Pedal couplerCOUPLER: A coupler allows the stops of one division to be played from the keyboard of another division.
DETACHED CONSOLE: A console separated from the rest of the organ, rather than built into the organ case.
DIVISION: A group of stops in an organ, playable as a separate entity (e.g. Great Organ, Swell Organ).
 DRAWSTOP : See Stop knob
reassembly of a drawstop actionDRAWSTOP ACTION: See Action
 ELECTRIC ACTION: 1. In its widest sense, any type of Action that uses electricity.  2. More strictly, a particular type of Action that uses an electromagnet to actuate a Pallet valve directly: also known as direct-electric or electro-mechanical action. Not to be confused with Electro-pneumatic action (see next entry).
ELECTRO-PNEUMATIC ACTION: A sophisticated type of power-assisted Action. When the organist presses a key, a low-voltage electric circuit is completed which activates an electromagnet in the organ: this in turn charges or exhausts one or more pneumatic Motors, thus opening the respective Pallet valve to admit wind to the pipes. An electric cable connects the console to the organ. The best examples of electro-pneumatic action are highly efficient and promote natural speech in the pipes.
FLUE/FLUE PIPE: 1. The opening for wind between the lower lip and the languid.  2 A pipe which produces its sound when wind passes through the flue and strikes the upper lip.
Solo Harmonic FluteFLUTE:  1. The term identifies a smooth-toned stop of low harmonic development produced by either stopped, half stopped or open flue pipes.  2.  In particular traditions, especially French, Flûte identifies a wide-scaled open flue with a narrow mouth and high cut-up.  Flute stops (in either sense) may appear at any pitch level.
Temple Church - boots for Cor Anglaise 1FOOT/PIPE FOOT: The bottom section of a flue pipe.  In metal pipes usually in the shape of an inverted cone, open at the bottom (the toehole) and almost completely closed at the top by the languid.  In wooden pipes the foot is usually a square or rectangular extension of the body with a cylindrical extension at the end of which is the toe.
 FRAME: See building frame
DSC00943smallFREE STANDING: This describes an organ which is entirely self-contained in its own case. It is supported on its own pedestal. Its case is free to resonate on all sides and on top.
Great pipeworkGREAT: The Great is the primary manual division of an organ.  Characterized by a principal chorus that establishes the primary characteristics of the sound of an individual instrument.
HOOD: The shape formed when the top of a pipe is mitred to turn it at an angle.  This prevents dirt from falling down the pipe and upsetting the tongue.  See also Knuckle.
KEY ACTION:  see Action
Charterhouse PedalboardKICKBOARD: The horizontal panel above the pedalboard, between the pedals and the lowest manual.  Expression pedals, coupler controls and toe studs may be located on or set into the kickboard.
Cheltenham College 32 ft reed Pipes and boots 6KNUCKLE: the shape formed when a reed Resonator is mitred to turn it through 360o. This gives the pipe extra strength, traps any dust, and allows it to fit within a restricted headroom.  See also Hood.
Ripon Cathedral - languids being solderedLANGUID: A horizontal plate that separates the body from the foot of a flue pipe.
MANUAL: The keyboard of an organ, similar to a piano keyboard and controlling its own set of pipes. Many organs have more than one manual, making it possible to move rapidly from one sound to another or to play a solo on one manual and accompany it on another.
 mechanical stop action combination machine (5)MECHANICAL ACTION: See Tracker action
Kings - Pedal mixture (5)MIXTURE:  Organ stops consisting of more than one rank of pipes.
MOTOR: A miniature bellows, used to provide motive force in Pneumatic and Electro-pneumatic actions.
Sloane Street - mouths of Great Double Open pipesMOUTH: The opening in the side of a flue pipe, where the foot joins the body.
Sloane St - removable palletsPALLET: A valve in the Windchest that admits air to the channel feeding the pipe when a key is pressed.
 PALLET BOX: The lower portion of a pallet and slider chest, from which wind is admitted to individual key channels by the action of pallets.
 PASSAGEBOARD: Passageway within an organ, used for tuning or maintenance.
PEDALBOARD: A special keyboard in the console designed to be played by the feet. Every organ has a Pedal, as it is needed to play the bass parts in organ literature.
PIPE RACK: A horizontal board located above the pipe chest, solidly fastened to the chest or to an adjacent vertical surface, and in line with a given set of pipes, used to support the larger pipes by means of ties or hooks. It also prevents accidental overturning of pipes during tuning and helps keep reed pipes in tune by reducing their tendency to move from vibration.
PIPES: These produce the sound and are constructed of either wood or metal. Each pipe produces a single tone, and it takes a series of them, one per key, to play the entire range of the keyboard. There are two classes of pipes; Reed pipes, which have a vibrating tongue producing the tone and a resonator to modify its quality; Flue pipes, with no moving parts except the air, like a whistle.
PNEUMATIC ACTION, or more specifically, Tubular-pneumatic action: An early type of power-assisted Action.  Pneumatic tubes connect the console to the organ. Two principles are used: 1. When the organist presses a key, a charge of wind is sent along a tube to inflate a pneumatic Motor which activates the Pallet valve to admit wind to the pipe .  2. Alternatively, the tube is exhausted, causing a charged motor to collapse. Restoration of pneumatic actions presents special challenges.
Royal Festival Hall - Positive TrumpetPOSITIF/POSITIV: A secondary manual division, unenclosed, usually containing a principal chorus that is of a smaller scale and based on a higher pitch than that of the primary manual chorus (Great).
 Pedal PrincipalPRINCIPAL: The primary tone color of the organ, produced by open flue pipes of moderate scale.  Voicing of principals varies in instruments from different places and different periods.  In different instruments, stops of principal tone color may be called Diapason, Principale, or Prizipal, or they may be identified only with a pitch designation, such as Fifteenth, Octave, or Decimanona.
Exeter Cathedral - racksRACKBOARDS: A method of supporting organ pipes.  A horizontal board with holes set above the upperboard.  Placing the pipes in the rackboard is called ‘racking in’.
Edington Priory - racking in Swell Flue (1)RANK: A set of pipes of similar construction, arranged on a windchest so that there is one pipe for each note of the keyboard which sounds the pipes.
Cheltenham College - 32ft reed pipesREED:  1. A pipe that produces its sound through the vibration of a tongue against a shallot.  2. In some uses, an alternate name for either tongue or shallot.
 REGISTRATION:  An organist’s choice of stops. 
RESERVOIR:  The lungs of the organ.  A wind reservoir was originally required to store the wind that was raised by pumping a Bellows.  Since the arrival of mechanical blowing (see Blower) storage is no longer necessary, but traditional reservoirs are still a respected method of controlling the wind supply from the blower and feeding it to the pipes at a steady pressure. A reservoir normally has either one or two sets of leathered ribs and folds – ‘single-rise­’ or (illustrated) ‘double-rise’.
RESONATOR:  The tube which forms the upper part of a reed pipe.
Hakadal - rollerboard (1)ROLLER: A mechanism in an organ with mechanical action for transferring motion from the key to a pallet located above and to the side of the end of the key.  Rollers are affixed to a “roller board,” typically a horizontal board, with its face parallel to the front of the keys.
SCALE:  The relationship between the diameter and length of the resonator of a pipe.
SHALLOT: A brass tube located in the boot of a reed pipe, against which the tongue vibrates to produce a sound.
SLIDER: A strip of wood or other material with holes that align with the pipe feet of a particular Stop on a Slider chest. The slider is movable and can stop the wind from entering the pipes located above it.
sliderSLIDER CHEST, or Slider soundboard:  A type of Windchest, the oldest in common use, valued for its musical benefits. It consists of a wooden grid with a wind channel for each note, and valves or Pallets to admit the wind to the pipes; the Stops being controlled by Sliders with holes corresponding to the pipe feet.  Much skill is required in the design and construction of a slider chest.
 SOLO ORGAN:  The fourth division of a four-manual organ, played from the top keyboard.
SOUNDBOARD:  an alternative term for Windchest.
 STICKER:  A strip of wood that carries the motion of the key to the windchest by a pushing motion, in an organ that is built with Tracker action. (Distinct from a Tracker, which has a pulling motion.)
STOP:  1. A set of pipes, all of similar construction, arranged on a Windchest so that there is one pipe for each note of the respective keyboard.  2.  The control which admits wind to a set of pipes, or ‘stops’ wind from entering – hence the term. (See also Stop knob.)
STOP ACTION (or Drawstop action): see Action
STOP KNOB, or Drawstop:  The control at the console which the organist pulls to select a particular set of pipes. Hence the expression ‘Pulling out all the stops’.
SWELL BOX, SWELL SHUTTERS:  In many organs one or more groups of pipes (e.g. Swell Organ, Solo Organ) are enclosed in a box with shutters, also known as shades or louvres, which can be opened or closed by the player to make a crescendo or diminuendo, using a swell pedal.
SWELL ORGAN:  One of the main divisions of an organ, enclosed in a Swell-box. Played from the top manual of a two- or three-manual organ
OLYMPUS DIGITAL CAMERASWELL PEDAL:  See previous entry.  Two swell pedals can be seen at the top centre of the photo (left).
Colchester - Viole d'Orchestre (6)TOE/TOEHOLE:  1. The lower end of the foot of either a flue or reed pipe, and the part of the pipe that is in contact with the chest.  The toe is usually made of lead, even in wooden pipes; the size of the toehole regulates the amount of wind that can enter the pipe.  2. Toehole: the hole in the topboard of a windchest that admits wind to a pipe.
Pedal Trombone tongues being fitted TONGUE:  A thin strip of brass that vibrates to produce the sound in a reed pipe.
Union Chapel, Islington - repairing trackersTRACKER:  A thin strip of wood (or sometimes metal) that carries the motion of the key to the windchest by a pulling motion in an instrument that is built with a Tracker action.  (Distinct from a Sticker, which has a pushing motion.)
trackerTRACKER ACTION, also known as Mechanical action:  The oldest form of Action, still used today and admired for the way in which it allows the player to control the speech of the pipesIt involves a system of rods (Trackers) and levers, whereby the player’s touch at the keyboard is transmitted directly to the valves which admit wind to the pipes.  See also Electro-pneumatic action.
West Abb - with some treble pipes in place8-9-8TREBLES: The smallest pipes in an organ.  The highest notes of a given stop.
Temple Church - wind trunkTRUNKS:  Ducts that convey wind through an organ,  Can be either of wood or metal.
TUNING: Tuning is the process of adjusting each pipe in the organ to the correct pitch so that they all sound in tune with each other. How the pitch of each pipe is adjusted depends on the type and construction of that pipe. The pitch is affected by temperature of the air in and around the pipes and tuning fluctuates with temperature changes so it must be re-done periodically so the organ sounds its best.
UPPER BOARD: The top layer of a windchest upon which pipes stand.
VOICING:  The art of adjusting the various parts of a pipe to produce the desired musical tone. The Voicer is responsible for the musical character of each instrument, preparing the pipes in the workshop and then adjusting each one in the building so that each rank has the appropriate balance with its neighbours and all combine to form a harmonious and exciting whole. A small organ will have several hundred pipes; a large one may have several thousand.
 WIND: The pressurised air which makes the organ pipes sound. See also Bellows, Blower, Reservoir.
WINDCHEST: The intricately-constructed box of wind upon which the pipes stand. It contains the mechanism which allows the wind to enter the pipes, depending on the notes played and the Stops selected by the organist. There are many different types – notably the Slider chest. An alternative term is Soundboard (regardless of the fact that an organ windchest is quite different in function from the soundboard of a piano or harpsichord).