Action: the mechanical connection between keys and pipes.

Balustrade: a rail and a row of balusters or posts that support it (as in a church gallery).

Bellows: a device used to pump air into the organ reservoir prior to electricity.

Blower: the enclosed, motor-driven fan that provides wind under pressure for the organ pipes.

Celeste: an 8' string stop composed of two pipes for each note, one being tuned slightly sharp to create an undulating effect.

Console: the unit that contains the manuals, pedalboard, pistons, etc.

Cornet: a wide-scaled compound stop without breaks, containing a third-sounding rank, often of short (treble) compass that was invented to sound like the brass cornet instrument.

Coupler: a contrivance by which any two or more of the ranks of keys, or keys and pedals, are connected so as to act together when the organ is played.

Crescendo pedal: a pedal which, when gradually depressed, brings on all or most of the stops of the organ progressively beginning with the softest.

Division: a self-contained part of the organ consisting of its own windchest, pipes, and keyboard.

Electric key action: an action in which a wire, an electrical circuit, and an electro magnet cause the valve below each pipe to open and close (See key action).

Façade: the face or front of an organ.

Great division: a grouping of pipes, normally not enclosed, played from the bottom manual of a 2-manual organ (or the middle manual of a 3-manual organ).

Hauptwerk (Great Organ): The majority of the organ's pipes, including those too large to fit elsewhere, constitute the 'Hauptwerk', often abbreviated to 'Werk.'

Key action: a mechanism the keyboard uses to control the pipe speech. This is accomplished by controlling the air flow to the pipes.

Manuals: keyboards of an organ.

Mechanical action: in mechanical action, there is one valve for each note on the keyboard. The key is connected to trackers that eventually connect to the valves that open to admit air from the wind chest into the pipes (See key action).

Organ case: the wooden housing around the entire organ or around one or more divisions of the organ that is often beautifully designed and carved.

Pedalboard: the structure on the floor that contains the pedals and the mechanisms that link them to the rest of the organ.

Pneumatic valves: valves, such as pallets below pipes, that are opened by air under pressure (See key action).

Positive division: a grouping of pipes similar to the Great division in that it is normally not enclosed, but of considerably lower dynamic level than the Great.

Principal: either of two types of open diapason organ stops, one of four-foot length and pitch and the other of eight-foot length and pitch.

Rank: a row of pipes operated by a single control known as a stop. Each row always has all pipes of the same kind of sound.

Reed pipe: an organ pipe with a strip of flat metal, called a metal tongue, placed against an open-faced shallot. Air forced into the organ vibrates the reed, causing a sound that is amplified by the resonator, the top, flared part of the pipe. Pitch is determined by the length of the tongue. Reed pipes have a strong, penetrating tone.

Scaling: the proportion of the width of a pipe to its length.

Speaking: a slang term that refers to organ pipes that make sound.

Stops: a stop is an individual voice in the organ, composed of one or more ranks of pipes.

Stop action: a mechanism that turns the stops on and off through the use of drawknobs on the sides of the console or stop tabs above the manuals.

Swellers: pedals that are connected to a shutter that controls the volume of a set of pipes on an organ housed in a box (swell box).

Temperament: the tuning scheme according to which the intervals between half-tones are adjusted to permit a variety of chords to be played on a keyboard instrument.

Tonal colors: sounds – both unique and imitative – made by a pipe organ.

Tracker action: a mechanical linkage between pipe organ keys or pedals pressed by the organist and the valve that allows air to flow into pipe(s) of the corresponding note (See mechanical action).

Tremulant or Tremolo: a mechanical device used to provide an undulation in the tone of the organ, through a rapidly recurring slight raising and lowering of the wind pressure.

Verdigris: the natural patina formed when copper, brass, or bronze is weathered and exposed to air or seawater over a period of time.

Voicing: the process of adjusting the parts of the pipe on the pipe organ to produce the desired tone.

Windchest: a plain wooden box on which the organ's pipes sit. When a stop is on, air flows from the reservoir into the box; when notes are played, it uses the air from this box to make the pipes speak.