Introduction I General description I Types of actions I Placement of the organ I Pitch levels available on the organ I Unification I Varieties of pipes I Principals (or Diapasons) I Flutes I Strings I Hybrids I Reeds I Mutations I Mixtures I Divisions of the organ I Couplers I Great I Swell I Choir I Positive I Solo or Bombarde I Echo or Antiphonal I Pedal I Tremolo I Pistons I Crescendo Pedal I Full Organ (Tutti or Sforzando) I Percussion I General characteristics of organ sound I Registration

Introduction:
The organ, as described by Mozart, is the 'King of instruments'. It is the largest instrument, the instrument with the most dynamic and pitch range, and is the loudest acoustical instrument devised by man. No pipe organ is alike. They can be a short compass, one manual organ with one set of pipes that can fit on a table to multi-manual giant that will take up several thousand square meters of floor space. Even 2 organs built alike will sound different because the acoustics of the room that they live in will affect the sound of each of them.

General description:
An organ is an acoustical, wind-blown, keyboard instrument. It ranges in size from a small instrument that can fit on a table and can be carried under one's arm, to one that weighs several tons. As the keys are played, and depending on what sounds are activated, it will activate mechanisms within the organ, and allow wind to be blown into the pipework, causing it to sound. Generally the organ has more than one keyboard so that the organist can pre-set different sounds on different keyboards to allow for a solo on one keyboard and an accompaniment on another keyboard or to be able to change sounds rapidly by going between different keyboards. The sound from the organ can range from very low to very high, and can range in color from sounds one would normally typify as 'organ sounds' to lush strings, sylvan flutes, and orchestral woodwinds.

Types of actions:
The action is how depressing the key or pulling the stop activate the playing of the pipe or activating the stop. Up until the 19th century, organs were exclusively operated by mechanical action. In other words, all of the connections between the different portions of the organ were accomplished with mechanical linkages. In the mid-19th century, an English engineer, Charles Spelleman Barker, devised a pneumatic devise to assist in the operation of mechanical action key action runs so organs could be run on higher wind pressure and the console could be detached from the main portion of the organ. Later in the 19th century, Edwin Horsell Pullbrook, an English organbuilder devised an action that transmitted the note and stop signals between the console and the chestwork through a series of tubes. The action was termed 'Tubular-pneumatic'. It was the first action which allowed the console to be remotely located from the remaining portions of the organ. At the end of the 19th century, electricity was developed to a point that it was usable for the pipe organ. Not only were organs now able to be winded from an electrically power blower (versus hand pumping the organ), but now the signals from the console to the remaining portions of the organ can be transmitted through wiring. Thus the advent of electric action. At first electric action was applied to windchests that were electrically activated, which in turn exhausted a series of pneumatic pouches. Stop action was controlled by allowing air into the channel under each individual stop. This first electro-pneumatic chest action was termed ventil chest. In the early 20th century, and different form of electro-pneumatic windchest was developed by Ernest M. Skinner, called a pitman chest, which uses a series of small valves to control the stop action. This allowed for a much faster and more reliable action. The last type of action developed was the electro-mechanical action which places an electric magnet with a valve attached to the magnet.

Placement of the organ:
Especially with the advent of electricity being introduced to the pipe organ, it allowed the organ to be placed practically anywhere in the building. With mechanical action organ, because of the direct mechanical attachment of the action, the console needed to be either attached directly to the remaining portions of the organ, or be mounted close to the organ. Long action runs meant that the action would be unduly heavy. Though normally it is recommended that the organ and its speaking parts be mounted on the long centre axis of the room, usually in the front of the room, and usually housed in some sort of casework. It has also been a custom in both the U.K. and North America to have some organs placed in chambers, generally along either side of the chancel area or on either side of the front of the building, and speaking out through casework or grills. Also for an echo effect, sometime there will be a division or divisions placed at the opposite end of the building, which could even be placed high up in the building near the top.

Pitch levels available on the organ:
The pipe organ has the greatest range of any acoustic instrument. From the low end of a 64' stop at 8 cycles per second to the top end of a 1' stop at over 20,000 cycles per second. A stops pitch range is based upon the lowest note of the rank, and is measured as the approximate length of the longest pipe. Thus an 8' set of pipes would have the longest pipe of the set approximately 8' long. Standard pitch (the same pitch for a given note as would be for a piano) would be the 8' pitch. A 16' stop would produce a pitch one octave lower than piano pitch, a 4' stop one octave higher than piano pitch, etc. Stops with fractional numbers (such as 2-2/3' or 1-3/5') produce pitches other than unison. These are used for producing different colour effects. Sometimes stops will have roman numerals such as an III or IV. These are Mixtures and the Roman numeral indicates the number of pipes playing at a time when a key is depressed.

Unification:
Sometime, especially with smaller instrument where space and cost maybe factors in determining the overall size of the instrument, an individual set of pipes in the organ, or the entire instrument maybe unified. This is done by taking an extended set of pipes and having it play at more than one pitch. Thus on a small unit organ a Flute rank, let's say, could make several stops of 16', 8', 4', 2-2/3', 2', 1-3/5', 1-1/3' and 1' all from the same set of pipes. This practice was especially prevalent in the theatre organs of the early 20th century. It is generally discouraged in classically designed organs, because it does not provide as much clarity of individual voices, and tonal variety.

Varieties of pipes:
Within a pipe organ there are several varieties of pipes. Generally they are divided into 2 broad, general groups: flue pipes and reed pipes. Flue pipes operate on a principal similar to a whistle, where as you blow into the end of the pipe, the wind pressure builds up in the foot of the pipe, which forces the airflow of the wind to strike the upper lip of the pipe, causing a sound which is strengthened and reinforced by the body of the pipe. Flue pipes can be divided into 4 families: Principals or Diapasons, Flutes, Strings and Hybrids. The other general group of pipes in a pipe organ is the reed pipes. Their operation is similar to that of an orchestral clarinet. When wind enters the foot of the pipe, the reed within the foot of the pipe begins to vibrate. The vibration of the reed strikes the shallot (which is similar to the mouthpiece of the clarinet) which creates the sound which is then strengthened and reinforced by the body (resonator) of the pipe. Reed pipes can be divided into 2 families: Chorus and solo, and these can further divided into full-length or fractional-length stops.

Principals (or Diapasons):
The principals or Diapasons are the backbone of the sound of the organ. Most people think of an 'organ sound' as a group of principals playing together. The pipes are open, and generally made of metal, which provides the sound generally used for accompanying singing, or playing larger pieces of organ music (for further description, and tonal examples please go to our stop dictionary).

Flutes:
The flutes of an organ are softer and darker than the principals. They are made from either wood or metal, and can be open, half open, or capped. Their tone can range from bright, singing and open like a flute in an orchestra, to dark, hollow and somber. They are generally used to accompany softer singing groups (such as a small chorus or a soloist) or for playing softer passages in music (for further description, and tonal examples please go to our stop dictionary).

Strings:
The string pipes of an organ are generally bright and keen sounding, imitating the sounds of stringed instruments. They are open pipes and can be made of either metal or wood. They are used for soft musical effects, and to imitate strings playing (for further description, and tonal examples please go to our stop dictionary).

Hybrids:
Hybrid stops are a cross between two types of flue families, such as a flute and string or flute and a principal stop. They lend characteristics of both families to the tone of the stop (for further description, and tonal examples please go to our stop dictionary).

Reeds:
The reed stops of an organ provide the power, colour and 'fire' of an organ. They can be chorus reeds, such as trumpets and tubas, which power and majesty, and are used for fanfares or to crown or cap the organ's sound. They can also be solo stops, especially orchestral imitating sounds such as Oboes, French Horns or English Horns. Full-length reeds emphasize the fundamental harmonics of a reed pipe, whereas fractional-length emphasizes the upper harmonics at the expense of the fundamental harmonic. Extremely short length reeds would include Regals and the Vox Humana stop(for further description, and tonal examples please go to our stop dictionary).

Mutations:
A mutation stop is a stop which plays something other then a normal pitch. Normally when you play a 'C' note, you would get a 'C' sounding pipe. But with a mutation stop when you play a 'C' note you would get a pipe sounding something other than a 'C'. Mutations are used for solo possibilities, to add color, and to add brilliance(for further description, and tonal examples please go to our stop dictionary).

Mixtures:
A mixture stop, used to add brightness in the bass, and fullness in the treble, is made of from a series of corroborating pipes. When a single note is played several pipes will play at once. The number of pipes is determined by a Roman numeral on the stop control (for further description, and tonal examples please go to our stop dictionary).

Divisions of the organ:
Generally most pipe organs have several divisions within the instrument. A division groups a series of stops that are specifically designed to work together to execute a specific function.

Couplers:
are controls within an organ that couple divisions together. The couplers can be divided into 2 groups, Intramanual and Intermanual. Intramanual couplers are designed to couple a division to itself at a different pitch level, such as Great to Great 4' (coupling the Great to itself an octave higher). Intermanual couplers are designed to couple one division to another (such as Swell to Great 8'). In this way, by the usage of couplers, the organ can become more versatile by combining sounds together.

Great:
Considered to be the main division of the organ. It usually contains the main Diapason chorus, primary chorus flutes, and a series of chorus reeds.

Swell:
Is generally considered the secondary division of the organ. It will contain a secondary Diapason chorus of a lighter quality, a secondary set of flute stops, usually a series of string stops, and a series of chorus and solo reeds. The division will be under expression.

Choir:
Usually contains stops in the organ used for accompanying choral groups or choral. These will include soft flutes and strings, and some orchestral solo reeds.

Positive:
A division usually used in the playing of baroque music. It will contain a tertiary diapason chorus of a light nature, bright flutes and upperwork, and imitative fractional-length reeds.

Solo or Bombarde:
A division usually big sounding stops intended for playing solo lines These will include large scaled diapasons, flutes, strings, large chorus reeds, and large orchestral solo reeds.

Echo or Antiphonal:
A division placed a distance away from the main organ, usually in a remote area of the building. These contain soft, and ethereal sounding stops such as flutes and strings.

Pedal:
This division contains the largest pipes of the organ, intended to provide the bass or 'bottom' to the organ. It will contain a variety of different stops to support the gamut of manual stops.

Tremolo:
An effect on an organ which causes pitch of the organ pipes playing to have a vibrato. This effect is especially useful in highlighting a solo line.

Pistons:
A series of buttons located underneath the keyboards used with the fingers, or around the pedalboard used with the feet, generally used to control pre-set combinations of stops. It is an aid to the organist, who can quickly change large combinations of stops.

Crescendo Pedal:
A pedal on the organ used to continuously add stops as the pedal is opened, and retracted as the pedal is closed. It is a way, by means of a pedal to gradually make the organ louder or softer.

Full Organ (Tutti or Sforzando):
With a single piston, it brings on all of the stops of the organ at once. Used for sudden climaxes.

Percussion:
Are stops within an organ that are non-pipe operated. They can be divided into 2 classes; tuned and non-tuned. Tuned percussion stops are ones that have distinct pitch, and are usually set in a scale comparative to the keyboard. Such would be chimes or bells. Non-tuned percussion stops have no distinct pitch, such as drums or cymbals.

General characteristics of organ sound:
The organ, being a wind blown instrument, has a unique sound of whistles of varying sizes and scales, and reed sounds of different qualities. It has a dynamic range from a whisper to a thunderous roar, as the loudest acoustical instrument known. Unlike any other classical, acoustical instrument, the pipe organ, in both a mechanical and tonal sense, has evolved over the centuries, not only regionally, but globally. The pipe organ more than any other instrument, as it has evolved has shaped and changed music and the way music has been composed. New schools of thought in organbuilding and tonal designs have launched and shaped all new schools of musical composition.

Registration:
Is the art form by which the organist selects the different sound colours which will be used for the music. Much as a composer selects the instruments of a symphony orchestra that will be used for a specific section of music, or even voice, the organist can select individual or a group of stops for a particular section of piece of music.

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