Pipe Organs in plain English

One thing that I noticed about the organ building industry is that a lot of terminology is somewhat inaccessible to the common person.  I’m here to try and remedy that.

Organ – a musical instrument that makes sound by blowing air through pipes.

Pipe – the part that makes sound when air is blown through it.  Comes in two flavors:  flue and reed.

Flue – the kind of pipe that works like a penny whistle – it makes sound by air blowing over a fipple (a tapered notch in the windway)

Reed (pipe) – the kind of pipe that works like a clarinet, oboe, or saxophone – it has a vibrating reed to make the sound.

Windway (1) – the narrow space at the mouth of a flue pipe that squeezes the wind down into a thin sheet to blow across the mouth to make the sound.

Windway (2) – any ductwork that carries slightly pressurized air (wind) to organ components.

Windchest – a mechanical box that has linkage to allow air into the proper pipes at the proper time.

Manual – a keyboard you play with your hands (looks like a shortened piano keyboard).  Sometimes only one, most times two or more per organ.

Pedal – a keyboard you play with your feet.  One per organ.

Division – a grouping of stops assigned to the same keyboard.  Names are usually Choir, Great, Swell, Positive, Echo, Antiphonal, and Pedal.  (Great and Swell being the two most common).

Stop – a series of pipes with the same tonal characteristics such that there is one (or more) pipe for each note on the keyboard.  Generally controlled with either drawknobs, rocking (tilting) tablets, or tongue-tablets.

Console – the desk that holds the keyboards and organ controls – where the organist sits to play the organ.

Rank – a series of pipes with the same tonal characteristics.  On mechanical (a.k.a. Tracker) action organs, rank = stop.  On electropneumatic or electromechanical action organs, a rank may be played by more than one stop (that’s called unification).

Mixture – a compound stop that plays more than one rank of pipes for each note.  Of principal tone quality.

Principal – a tonal quality produced by open diapason pipes.  The unique and characteristic sound of the pipe organ.

Diapason – a type of flue pipe of moderate scale that produces a non-imitative sound called a Principal tone quality.

Flute – a type of flue pipe of wide scale that produces a flute or woodwind-like tone quality.

String – a type of flue pipe of narrow scale that produces one of two tone qualities:  Non-imitative or imitative.  Non-imitative strings produce a cutting, assertive sound.  Imitative strings produce a sound like an instrument in the violin family (cello, viola, etc.).

Coupler – an organ control that allows the organist to play the pipes from one division on another division’s keyboard.  Example:  the Swell to Great coupler allows the organist to play the pipes from the Swell division on the Great manual.

Scale – a quality of flue pipes that specifies the relationship of the diameter of the pipe to the resonating length of the pipe.  It’s the largest key factor that determines how a pipe will sound.

Action – the mechanism by which the organ functions – the process that allows the organ to make sound when a key is pressed.  Types are Mechanical (a.k.a. Tracker), Electropneumatic, and Electromechanical.

Tracker Action (a.k.a. Mechanical Action) – each key is connected directly to the windchests by a series of levers called trackers.  The trackers connect to spring-loaded wire shafts in the windchests called pulldowns.  The pulldowns connect to pallets – leather-covered stoppers that prevent air from entering the pipes except when the correct keys are pressed.

Electropneumatic Action – the keys have electronic contacts that, when activated, open and close a series of stoppers (called Barker Levers) via solenoids that create negative pressure in special wind channels (called pneumatic relays) that connect to the windchests.  This negative pressure actuates air cells called pneumatics that open and close the pallets that allow air into the pipes.

Electronic Action – the keys have electronic contacts that connect to key control channels on an organ controller – a computer that makes the decisions about what pallets need to be opened based on what other organ controls are turned on (like stops, couplers, etc.).  The controller action channels connect to solenoids that open and close the pallets at appropriate times.


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