There are two types of action that determine which pipes will sound: the stop action, and the key action (see Actions and Wind).

Other types of action are the combination action, and that used to open and close the shutters of the swelll box.

This term is also used to describe the touch characteristics of a keyboard.

A pneumatic lever used in some organs with mechanical key action to reduce key resistance. Introduced during the mid-19^th century to deal with increasing wind pressures.

Use of the same rank in more than one division to reduce the number of pipes required. See Borrowed Stop.

In early music, a term used for a melody used as the basis of polyphonic composition. On the organ, this would typically be played with the Choralbass.

The term given to the puff of wind produced when a pipe starts to speak (which sounds something like a cough). In an organ with mechanical key action, it can be controlled by varying the force with which the key is hit.

Triggered by pistons that are pre-programmed with stop combinations. This action changes the combination by physically moving the stop controls involved. This both enables stop controls and pistons to be used interchangeably, and gives the organist visual indication of the effect.

A means of combining two divisions of the organ by uniting keyboards. See Coupler.

Available mainly on larger organs to change the volume by successively adding or removing stops in a predetermined sequence.

The English word for principal, used for an open flue stop of medium scale and normally unison pitch (synonymous with open diapason). It is also commonly used to denote the scale of a flue pipe as medium (rather than flute or string), even though the stopped diapason is flute-scale. Grove offers four definitions; the third and only organ-specific one is: In classical British organ terminology, 'the diapasons' (Stopped and Open) form the foundation upon which the Great Organ flue choruses may be built. See Principals.

A set of stops normally associated with a keyboard, but may also be a floating division. See Division.

A pedal (swell or crescendo) that allows the volume to be continuously adjusted while playing. See Expression Pedals.

Normally found only on large organs, this is a division that is not normally connected to a keyboard, but may be connected to the required keyboard when needed by means of a Coupler.

The most commonly used class of organ pipe, that produces sound without moving parts. See Flue Pipes.

A flue pipe of wide scale. See Flutes.

Grove states that this term applies to all stops at unison or octave pitch (the entire scope of Pipe Types and Stops). However, the French equivalent fonds d'orgue includes only unison/octave flutes and principals at up to 4' pitch. So perhaps a definition of this term is best left to the reader's interpretation, based on the way it is used.

A series of integer multiples of the fundamental frequency; the presence of these give musical instruments their specific timbre. See Harmonics.

This is the name of the main manual on a German organ, but also the name of virtual organ software; see the producer's website. The software most similar to it is GrandOrgue.

One of the two actions of the organ, operated by the keys on the manuals and pedals. See Stop and Key Actions.

This normally operates on a Division of the organ, and may be played either with the hands or with the feet. See Keyboards.

Another name for kneeboard.

Vertical panel behind and above the pedalboard. See Kneeboard.

The delay between sound being initiated such as by a keypress, and it being produced (system latency) or heard (total latency). In a pipe organ (with the possible exception of those with pneumatic action), most of the latency is usually due to the time the sound takes to travel from the pipes to the organist. In a computer-based organ used in the home, nearly all latency is normally due to buffering of the audio output. See Latency.

An organ keyboard for the hands. See Manuals.

(Musical Instrument Digital Interface) a protocol developed in 1983 to transfer signals from devices such as keyboards and (in the case of the organ) expression pedals. Used extensively by virtual organ software as well as the more recent digital and pipe organs. See Connecting MIDI.

An organ stop comprising several ranks. See Mixture.

An organ stop comprising a single rank at non-octave pitch. See Mutation.

A flat (not raised) note on a keyboard (typically white on a manual). See Keyboards.

A keyboard for the feet. See Pedalboard.

A control located either under the keys of a manual (when it is known as a thumb piston), or on the kneeboard (when it is known as a toe piston). Most are used to activate a pre-pogrammed stop combination, but some give quick access to other functions.

The number of voices that sound at once. In a pipe organ, this is the number of pipes that speak simultaneously. In a virtual organ (where multi-rank stops such as mixtures count as a single voice) it is the number of stop/note samples that are to be handled simultanously; this also includes release samples that contain the reverberation once the pipe has stopped speaking.

A type of organ that can be carried.

An organ that can be moved, and would normally have ranks no greater than 4' physical length. Also used for a division of an organ that produces a similar sound.

A flue pipe of medium scale, in between flute (wide scale) and string (narrow scale). Also the standard stop name for that type. See Principals. In English, commonly called diapason.

Refers to intervals that correspond to the harmonic series - see Harmonics. For example, a pure perfect 5th has the frequency ratio 3/2, while in equal temperament it is somewhat impure at about 1.4983.

A row of pipes producing the same type of sound. See Rank.

One of two commonly-used classes of organ pipe, that produces sound by means of a vibrating metal tongue. See Reed Pipes.

The art (unique to organists) of creating an appropriate sound by combining the available stops. Also refers to the selected combination(s) of stops. See Stop.

An organ stop comprising two ranks that produces a difference product. See Resultant.

The set of recorded sound samples, and other data such as images and the organ definition used to implement a virtual organ. See Sample Sets.

In a flue pipe, its diameter in relation to its speaking length (see scale).

Also used to refer to the key spacing in a keyboard (manual or pedal). While usually standardized, it may vary considerably in pedalboards that do not comply with the standards.

A raised note on a keyboard (typically black on a manual). See Keyboards.

A control found with the Stop Controls that is involved with the stop action (i.e. in opening one or more ranks of pipes).

This may refer to either a speaking stop (see also Stop) or to an accessory stop.

One of the two main actions of the organ, operated by the stop controls on the console. See Stop and Key Actions.

A flue pipe of narrow scale. See Strings.

A chamber with shutters, used to enclose a division of the organ so that the volume may be changed using a swell pedal. See Enclosed Division.

A pedal that allows the volume of an enclosed division to be changed by opening and closing the shutters of the swell box.

The application of adjustments to pure intervals to make them align with the 12-note chromatic scale. See Temperament.

A piston located under the keys of the manuals.

A piston that is operated by the feet (also known as Toe Stud).

A type of accessory stop that produces sound effects not involving pipes (for example, percussion and bird song).

Mechanical key action, in which key presses are transmitted by means of rods of wood, aluminum, or other material.

A wavering effect created by varying the wind supply. See Tremulant.

An organ stop comprising two ranks, one slightly detuned of the other. See Undulating.

The creation of stops of different pitches using the same rank. See Unified Stop.

A large valve that opens/closes the airway to a wind chest. In a few organs (especially late 19^th century French ones), this could be operated by a pedal to turn on/off a set of stops such as reeds and mixtures.

This is an organ that generates sound by combining in real time recorded samples from one (or possibly multiple) real organs. See Why a Virtual Organ?.

The art of adjusting an organ pipe so that it produces the required quality and quantity of sound, and is consistent with other pipes in the rank. This is firstly done in the workshop, using a small organ known as a "voicing rack". Final voicing (known as "finishing") is done after installation, and may take several months for a large organ. Different types of adjustment are required for Flue Pipes and Reed Pipes.

The pressurized air fed to the pipes. Wind pressure is normally measured in inches of water. It is typically around 3", but may be much higher (up to 100") for some reeds.

The container of pressurized air on which the pipes stand.