A short dictionary of pipe organ terms

These are the original German terms. Where an English equivalent exists, it is shown in brackets.
Balgen (Bellows) Originally, bellows produced the air supply for the pipes. Today, fans are used, giving a constant air stream, and most old organs have changed over to this system.
Blockwerk From the 14th. to the 16th. century, before the division of the organ into independent sound-producing sections, different rows of pipes could only sound together. These linked rows of pipes are known as 'Blockwerk'.
Brustwerk A section of shorter pipes built directly above the organist, below the Hauptwerk (Great Organ).
Disposition (Arrangement) Technical term for the design and layout of an organ's mechanism and pipes, indicating the number and type of pipe sections ('Werke')
Elektronische Orgel (Electronic Organ) Also known as home organs, these miniaturized instruments, some with pedals (in most cases, a limited range of short sprung levers, known as 'Stummelpedal'), still use some of the terminology of the huge pipe organ ancestors. For economic and practical reasons, they are often used in small halls and churches. Perhaps the best known home organ performer is Britain's Eric Mc. Whirter, 'Scotland's J.S. Bach'.
Fusslagen (measurement in feet) The old measurement for organ pipe construction is the foot - 8', 16', etc. A 'foot' varied from country to country and in different eras, somewhere between 26,5 and 30,5 centimetres. Since the Middle Ages, the height of a pipe was set at 8' for C0 (Middle C is C3), 4' for the octave above, 16' for the octave below (etc.). Other intervals are achieved by fractions, for example, 5 1/3' for a fifth, 2 2/3 ' for a twelfth, etc.
Gedackte Pfeifen Pipes which are closed at the top. They sound an octave lower than open-topped pipes of the same length.
Gemischte Stimmen (Mixed voices) A combination of sounds chosen by the organist and played from one manual.
Hauptwerk (Great Organ) The majority of the organ's pipes, including those too large to fit elsewhere, constitute the 'Hauptwerk', often abbreviated to 'Werk'.
Holzpfeifen (Wooden pipes) In contrast to the metal pipes, wooden pipes have a square (very occasionally triangular) cross-section, and give a very soft, quiet sound. They are often included in the main pipe display, not for their acoustic properties, but because of their decorative potential.
Koppel (coupling) The mechanical combination of different voices of the organ, as in 'Basskoppel', 'Melodiekoppel' and 'Manualkoppel'. As a rule, coupling links a louder sound to a weaker one to produce a stronger combination tone.
Labialpfeifen (aka Lippenpfeifen) (Lipped pipes) These comprise the majority of organ pipes, and are made of metal or wood. The metal pipes are cylindrical, conical or funnel-shaped, and can be open or closed (gedackt) at the top, giving a number of different possible combinations. The wooden pipes have a square or rectangular (very rarely, triangular) cross-section.
Lingualpfeifen Also known as 'Zungenstimmen' (reed stops) or 'Schnarrwerk', these are the second most important organ pipes after the 'Labialpfeifen'. They have free vibrating reeds which are activated by the air stream.
Manual Each set of pipes has its own keyboard, called a manual. Generally speaking, church organs have two or three manuals, each with a span of 5 octaves.
Mixtur (Mixture) A higher pitched set of pipes used to add brilliance and penetration to the full organ sound - these are often pitched an octave, octave plus fifth, or 2 octaves plus a third above the original pitch.
Oberwerk see 'Schwellwerk'.
Pedal A special keyboard for the feet, consisting of about 30 sprung levers. Pedal is also the name for the section of pipes connected to these foot pedals. By activating the 'Pedalkoppel' these pipes can be played from a manual.
Pfeifen (Pipes) In the early Middle Ages, made from bronze, copper or wood, later from tin, lead or metal alloys, occasionally also from ivory (in the 'Prospekt', or main organ display). The lengths of pipes is given in feet. Large church organs can have as many as 6000 pipes, some as long as 30 metres.
Positiv A type of small, versatile organ dating from the 19th. century. Later, certain sets of pipes ('Werke') in large church organs were named 'Positiv', for example 'Rückpositiv' and 'Seitenpositiv'.
Prinzipal (Principal) Originally, a name given to all the 'stops' (see below) connected to the 'Blockwerk'. Later, 'Principal' came to mean a particular stop with a strong sound, suitable for soloing.
Prospekt The main visual display of the organ. The wooden sections of the 'Prospekt' are crafted with great skill, and valuable materials such as brass, pewter (pure tin) and ivory are used for the pipes section.
Register (or 'Stimme') Term for the individual sounds of the organ, similar in concept to a synthesizer 'program'. Also refers to the mechanism (Stop) which activates the different group of pipes.
Rohrflöte (Reed pipe) A cylindrical pipe with a small tube welded into its closed top section. The length of these pipes varies in proportion to their diameter, giving different shapes and sounds.
Rückpositiv (Choir organ) A set of pipes built behind the organist. Developed for accompaniment of the choir, this is in effect a smaller, quieter organ with its own dedicated manual positioned below that of the main organ. Hidden from the congregation by the Rückpositiv pipes, the organist can concentrate on his or her performance!
Schwellwerk (Swell organ Pipes enclosed in a cabinet with moveable wooden shutters or lids - these may be opened and closed by pedal control to vary the volume of the pipes.
Stumme Pfeifen (Mute pipes) Also known as 'blind pipes', these produce no sound but are included in the Prospect for visual symmetry.
Windlade (Wind chest) Box underneath the organ containing the air supply apparatus. Through this,the air stream is diverted to the appropriate pipes, depending on stop selection.
Ventilatoren (Fan or air blower) Today, these replace the bellows. Electronically operated, they maintain an even supply of air to the pipes.
Zungen (Reeds) Name of the small membranes made out of springy pieces of metal, which are fixed in one end of an organ pipe. Some vribrate freely, others buzz against the interior of the pipe. The reeds are activated by the air stream, and the notes produced are greatly amplified by the pipes. A great many organ registers rely on these reed pipes (see 'Lingualpfeifen' above).