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American organ   A type of reed organ which is similar to the harmonium but differs in one respect. The reservoir contains a vacuum rather than positive air pressure, so air is drawn throught the reeds into the reservoir, rather than being blown out through the reeds. The sound quality tends to be less dramatic, but softer and more controllable.

Analogue organ  A type of electronic organ using an older form of technology. The word "analogue" distingishes it from the later  "digital" electronic organs.

Bach, Johann Sebastian   One of the greatest of all composers. His organ playing abilities were legendary during his lifetime, and he left a large volume of compositions of outstanding merit which could be said to form the "core" of the instrument's repertoire. Ironically, it now appears that the most famous of all his organ works Toccata and Fugue in D minor may well have been written by someone else!

Cavaille-Coll, Aristide   French organ buider of the 19th century of enormous importance to the history and development of the organ. He increased the power and tonal range of the instrument, and the quality of his work caused many leading composers of the time to take the organ very seriously indeed. Built to last, many of his instruments have survived more-or-less unaltered and are still a source of delight to all who are fortunate enough to play them.  

Choir   One of the standard divisions of a pipe organ. Usually present in British organs having three or more manuals and situated immediately below the Great manual. The common-sense assumption that this division is intended for accompanying the choir turns out not to be true. Instead, "choir" is believed to be a corruption of "chair", which refers to the practice of locating the pipes of this division behind the organist's seat.  

Clavier   Alternative name for  "keyboard".

Combination  In organ terminology, the word "combination" refers to the collection of stops which are selected ("drawn") at any particular time. Stops may be combined in any way the performer chooses, but some combinations will be far more satifactory from a musical point of view than others! As any mathematician will tell you, the number of possible combinations is far greater than the number of stops. For example. a one-manual organ with only four speaking stops would provide a total of 15 possible combinations (not counting the silent one in which all stops are OFF).  As the number of stops increases, the number of possible combinations rises dramatically. Better equipped organs allow combinations of stops to be accessed directly using thumb or toe pistons. This provides the performer with a higher level of control (compared to operating the stops individually) and makes it possible to have frequent changes of registration during the course of a piece of music.

Computer organ   See "Digital organ".

Console  Collective names for the organ's controls. The console therefore includes the manual and pedal keyboards, the stops and pistons, the music stand, the bench, etc. Sometimes the console is quite separate from the main body of the organ, in which case it is known as a "detached console".

Coupler  A device which allows more than one division of an organ to be played from a single keyboard. The coupler is controlled from the console by a draw-knob or other form of control, and is labelled with the names of the divisions which are being connected. For example when the "Swell to Great"  coupler is drawn, the Swell division can be played from the Great keyboard (but not the other way round).  Sometimes couplers play notes an octave above or below, either on the same of a different keyboard. On older organs, the coupling is carried out mechanically, which has the disadvantage of increasing the finger pressure required to depress the key.

Diapason   One of the commonest of all pipe organ stops. The diapasons form the "foundation" of the organ's tone.  They consist of flue pipes which may be either open or stopped.

Diapason chorus   Most organs have a number of ranks of diapason pipes at different pitches. When played together they create the rich harmonics of the "full organ" sound.

Digital organ   A later type of electronic organ, using a different type of technology from the earlier "analogue" type.  There were also known as "computer organs" for a while.

Division  All but the smallest pipe organs are organised into a number of parts or "divisions". Except for sharing a common air supply, each division is effectively a self-contained pipe organ in its own right, with its own keyboard (or pedalboard) and its own set of stops.   In British church or classical organs, commonly used names for the divisions are Swell, Great, Pedal, Choir, Echo and Solo. A "coupler" (q.v.) allows more than one division to be played from the same keyboard. The theatre organ is organised rather differently. The ranks of pipes may be located in two or more separate chambers (ofen called "main" and "solo") but there isn't a simple one-to-one correspondence between chambers and keyboards.

Equal temperament   See "Temperament"

Facade   The part of an organ's case which is open to view, usually featuring a number of organ pipes, possibly highly decorated. People often assume that all the pipes which are  displayed are dummy pipes, but it is usually the case that most, if not all, are pipes which speak. If you're going to have the pipes there anyway, you might as well make use of them!

Flue pipe   The pipes of a pipe organ can be subdivided into two families: flue pipes and reed pipes. The flue pipe is the more familiar type,  often visible as part of the organ's facade. They may be made of metal or wood and me be open or closed at their upper ends. Flue pipes are used for diapason and related stops (the "foundation" of the organ) as well as for flute and string toned stops. Generally speaking, they are weaker in harmonics than reed pipes, but this can be compensated for by combining ranks of different pitches to form a chorus with a richer harmonic structure. To that extent, the pipe organ could well be described as the earliest form of synthesiser!

Great   One of the standard divisons of a pipe organ. As its name suggest, the Great division contains some of the loudest stops of the organ, including the main diapason chorus and (usually) at least one loud reed stop such as "trumpet" or "posaune".  In the majority of cases the Great division is unenclosed - there is no means of expression but the pipes speak with maximum volume and clarity. In British organs, the Great is usually the lower keyboard of a two manual instrument, or the middle keyboard of a three manual one.

Harmonium   A type of reed organ in which pressurised air from a reservoir is forced out through free reeds to produce sound.  In the late 19th and early 20th century the harmonium was at the cutting edge of musical technology and looked upon fondly by a number of eminent composers. Gradually, it fell out of favour, but has enjoyed something of a revival more recently.

Hauptwerk  A leading brand of virtual pipe organ software supplied by Milan Digital Audio. Available in "free", "basic" and "advanced" versions.  There are now a considerable number of Sample Sets available for Hauptwerk, many from third party suppliers, covering organs of all sizes, styles and periods.

Manual   An alternative name for an organ's keyboard. Actually a contraction of "Manual Keyboard" which emphasises that this is a keyboard for the hands rather than the feet. Organs are often classified by the number of keyboards they possess - eg many medium sized church organs would be "two manual and pedal". The smallest organs have  a single manual, the largest have 5, or even more in rare cases. The standard compass for classical organs is 5 octaves c-c (61 notes) but many older organs have shorter keyboard (eg 58 notes), while some reed organs had a five octave compass starting on f. Home electronic organs often have considerably shorter keyboards which are staggered

MIDI   An agreed standard protocol which allows electronic musical instruments and other devices to communicate with each other. The MIDI standard is essential for virtual pipe organs, allowing keyboards, pedalboards, computers and software products from various  manufacturers to work together as one.

Miditzer   Leading brand of virtual theatre pipe organ.  Unlike Hauptwerk, which can load a range of organ sample sets, Miditzer is devoted to one particular organ, the Wurlitzer theatre organ. The two manual version can be download for free. The three manual version has a 60 day free trial period after which a donation is required.

Open pipe   A flue pipe which does not have a stopper at its upper end.  The column of air in the pipe is in contact with the surrounding air.  This influences which harmonics are present.  Open pipes tend to produce a more robust sound.  Sometimes, the word "open" is engraved on the stop control, eg Open Diapason 8'.

Pedalboard   The part of an organ's console which allows notes to be played by the performer's feet. Actually a contraction of "Pedal Keyboard". Not all organs have pedalboards. The standard compass for classical organs and theatre organs is c-f (30 notes) or c-g (32 notes). Many home electronic organs have a just single octave of pedals (13 notes) - a few have 25 notes.  Pedalboards can be either flat or concave, and either parallel or radiating. The radiating, concave pedalboard has become the norm as it best accomodates the natural movements of the performer's legs and feet.

Piston   A  push switch used to control some aspect of the organ's functioning. There are two types: thumb pistons and toe pistons, depending on which part of the organist is used to operate them. Thumb pistons are located just below the manual keyboard(s) and toe pistons just above the pedalboard. The idea is so they can be operated with minimum disruption to the playing. They are used mostly for combinations (q.v), also to activate couplers and for other special effects.  

Rank   A row of organ pipes voiced to have a particular musical character. As each organ pipe is only capable of producing a single note, a rank normally contains as many pipes as there are keys on the keyboard. Each pipe is a different length - the longer pipes give the lowest notes and the shortest the highest. To some extent, the word "rank" is interchangeable with the word "stop". In many church organs, each (speaking) stop of the console will have a corresponding rank of pipes which it controls. However, this is not always the case, as it is possible to use a given rank of pipes for more than one stop, particulalrly if the rank is extended in length. This is particularly true of the theatre organ where a relatively small number of ranks is used to provide a large number of stops.

Reed organ   While the pipe organ usually contains Reed stops, the expression "Reed organ" usually denotes a slightly different type of instrument - one which uses the "free reed" which was developed during the 19th century. Harmoniums (or should that be harmonia?) and American Organs are both examples of reed organs. They were usually single keyboard instruments pumped by the player's feet, but two manual and pedal reed organs were also made, these being hand-pumped by an assistant or (later) blown by electrical means. Other free reed instruments are the accordian and the harmonica.

Reed pipe   The pipes of a pipe organ can be subdivided into two families: flue pipes and reed pipes. The reeds are less familiar, not usually appearing as part of the organ's facade. In appearance they usually comprise a box at the base with some sort of resonator mounted on top.  The type of reeds used in a pipe organ are "beating reeds", and should not be confused with the "free reeds" which are used in harmoniums, accordions, etc. Reed pipes tend to be naturally rich in harmonics, and produce sounds not too far removed from the woodwind and brass sections of an orchestra. They are often named accordinly: Oboe, Clarinet, Trumpet, Trombone, etc. Some are relatively quiet solo stops, while others are designed to make a powerful contribution to the sound of the full organ.

Registration   This word describes the way in which the stops of the organ are used to control the volume and tonal quality of the sound produced. Pipe organs differ greatly - each has its own musical personality  - so before giving a recital on an unfamiliar instrument, a performer will go through the music which is to be played selecting appropriate stops for each part (to some extent by trial and error) until a satisfactory sound is achieved. This activity is known as "registering" the music, and is the organ equivalent of orchestration. The organist lacks some of the means of expression avialable to other instrumentalists, but skillfull registration ensures a performance will be full of colour and variety, from moments of profound calm and tranquility to thrilling, thunderous climaxes.

Sample Set - The digital information which is loaded into virtual pipe organ software in order to reproduce the sounds of a particular organ. Sample sets are often created by sampling the sounds of a real-world organ, often on a pipe-by-pipe basis. They can also be created synthetically, or by combining parts of existing sample sets. 

Stop   This word is used in two ways, first to mean one of the "voices" of the organ, and secondly to mean the drawknob, tab switch or other device which is used to control that particular voice. Stops are defined by a name ( Diapason, Hautbois, Celeste, etc) which describes the tonal characteristics, and by a length (16 foot, 8 foot, 4 foot, etc) which describes the pitch, this information being engraved on the knob or switch. Sometimes the expression "Speaking stop" is used, to distinguish this type of control from the purely mechanical ones which couple together different keyboards, switch on tremulants, etc.  An important part of the organist's art is to use the stops with sensitivity and intelligence, so that the sound produced by the instrument is appropiate to the music being played. 

Stopped pipe   A flue pipe which has a stopper at its upper end.  The column of air in the pipe is cut off from the surrounding air, influencing which harmonics are produced.  Stopped pipes tend to have softer, flute-like tone. They also sound an octave lower than an open pipe of the same physical length.  The engraving of the stop control always refers to the pitch, rather than the physical length.  A rank labelled Stopped Diapason 8'  would produce notes at the same pitch as one labelled Open Diapason 8', but the pipes would only be half as long. In other words, the longest (lowest) pipe would be approximately 4' in length, rather than 8'.  The stopper of a stopped pipe provies a convenient means of tuning it.

Swell   One of the standard divisions of a pipe organ. In British organs, the swell manual is usually positioned immediately above the Great.  The distinguishing characteristic of the swell division is that it is  effectively built into a room ("enclosed"), one of the walls of which is provided with shutters controlled by a pedal to adjust the volume of sound produced. This provides the performer with a means of expression.

Swell pedal   Also sometimes known as "Swell shoe". This pedal, usually positioned centrally just above the organ's pedalboard controls the shutters of the swell department and providess the organist with a means  of expression. "Swell pedal" is often used generically to mean any sort of expression pedal.

Temperament   In the context of musical instruments, this refers to the method of tuning which is used.  It's an unfortunate fact of life that it's impossible to tune an instrument so it sounds perfect in every key. In the past, methods of tuning were used which made instruments quite unplayable in certain keys. Nowadays, the "Equal Temperament" system of tuning is almost universal  (for organs and other instruments). This is a compromise  solution which distributes the imperfections equally between  the keys. The advantage is that all keys are equally playable, the disadvantage is that they all sound the same which is slightly boring.  Hauptwerk defaults to equal temperament, but allows the user to select alternative temperaments if required.

Transcription   An arrangement which allows a piece of music to be played on different instrument(s) from the one(s) it was written for.  In an earlier age, organ transcriptions were a popular means of bringing orchestral or operatic music to a wider audience.  Edwin Lemare wrote a number of famous transciptions for the organ, including Wagner's Ride of the Valkerye. While it obviously takes much skill to transcribe a full orchestral score, other types of music can be transcribed relatively easily. For example, in the case of a song with simple piano accompaniment, the organist's right hand can take the vocal part, while the piano part is divided between the left hand and the feet.

Tremulant  In pipe organs, a mechanical device which creates a controlled oscillation of air pressure, and gives a trembling quality to the sound. Loved by some, hated by others. In classical organ music, it is customary to play mostly without the tremulant, and to use it but sparingly for special effects. The theatre organ tradition is to use the tremulant(s) most of the time. In pipeless organs the same effect can be created  electronically.

Tuning  The art of adjusting organ pipes to sound at the correct pitch.  Flue pipes are tuned by altering the effective length of the pipe. With stopped pipes, the stopper is moved up or down, open pipes are fitted with adjustable tuning slides or a flap is bent back from the top of the pipe. Reed pipes are usually fitted with a wire for tuning purposes. Pipe organs are susceptible to changes in temperature and humidity, and need tuning on a regular basis. One of the advantages of digital electronic organs is that they never require tuning.

Virtual Pipe Organ   A software product which allows a pipe organ to be simulated on a personal computer. The sound of the original instrument is accurately reproduced, often by sampling each pipe individually. At the same time the computer screen displays an  image of the computer's console, complete with keyboards, pedals, stops etc which the user can operate using the computer's mouse. As such it provides a valuable educational tool to increase understanding of the way an organ works. However, if MIDI keyboards and a MIDI pedalboard are connected to the computer, the Virtual Pipe Organ becomes a serious musical instrument. For reasons of cost and flexibility it is now a serious rival  to the off-the-shelf digital classical organ, and is likely to increase in popularity in the future.

Voicing   The art of manipulating the physical parts of an organ pipe (eg by bending or nicking) until the required tone is achieved.  Voicing is a completely different process from tuning (q.v.).  usually carried out at the organ builder's works. It is a highly skilled art requiring an acute musical ear.

VPO   Commonly used abbreviation for Virtual Pipe Organ

VTPO   Commonly used abbreviation for Virtual Theatre Pipe Organ