No__104__The Organ from Encyclopædia Britannica, Inc.

[Peter Anderson]

The following is taken from Encyclopaedia Britannica, Inc. and has further additions to explain some terms in blue type, also taken from Britannica, Inc.

You can read through these posts, by just concentrating on the black type, and ignoring the blue type completely.

As it is quite lengthy, it is posted in a series of 17 parts, to enable you to handle each part in manageable portions.   Each of these parts will initially be posted every couple of days.

I thought this was interesting (at least for some) and runs neatly alongside these other Peters Pearls, for which these are the appropriate links

#103 A brief history of the electronic organ:

http://www.ar-group.org/smforum/index.php?topic=3265.0


and #83 How does a Pipe Organ work?

http://www.ar-group.org/smforum/index.php?topic=3012.0




The Organ

Part 1

An organ is a keyboard instrument in which sound is produced by pipes or reeds to which wind is supplied through a mechanism under the control of the organist.

{Musical sound, any tone with characteristics such as controlled pitch and timbre. The sounds are produced by instruments in which the periodic vibrations can be controlled by the performer.
That some sounds are intrinsically musical, while others are not, is an oversimplification. From the tinkle of a bell to the slam of a door, any sound is a potential ingredient for the kinds of sound organization called music. The choices of sounds for music making have been severely limited in all places and periods by a diversity of physical, aesthetic, and cultural considerations. This article will analyze those involved in Western musical traditions.
The fundamental distinction usually made has been between tone and noise, a distinction best clarified by referring to the physical characteristics of sound. Tone differs from noise mainly in that it possesses features that enable it to be regarded as autonomous. Noises are most readily identified, not by their character but by their sources; e.g., the noise of the dripping faucet, the grating chalk, or the squeaking gate. Although tones too are commonly linked with their sources (violin tone, flute tone, etc.), they more readily achieve autonomy because they possess controlled pitch, loudness, timbre, and duration, attributes that make them amenable to musical organization. Instruments that yield musical sounds, or tones, are those that produce periodic vibrations. Their periodicity is their controllable (i.e.,musical) basis.
The strings of the violin, the lips of the trumpet player, the reed of a saxophone, and the wooden slabs of a xylophone are all, in their unique ways, producers of periodic vibrations. The pitch, or high-low aspect, created by each of these vibrating bodies is most directly a product of vibrational frequency. Timbre (tone colour) is a product of the total complement of simultaneous motions enacted by any medium during its vibration. Loudness is a product of the intensity of that motion. Duration is the length of time that a tone persists.
Each of these attributes is revealed in the wave form of a tone. The pattern may be visualized as an elastic reed—like that of a clarinet—fixed at one end, moving like a pendulum in a to-and-fro pattern when set into motion (see illustration). Clearly, this reed’s motion will be in proportion to the applied force. Its arc of movement will be lesser or greater depending upon the degree of pressure used to set it into motion. Once moving, it will oscillate until friction and its own inertia cause it to return to its original state of rest. As it moves through its arc the reed passes through a periodic number of cycles per time unit, although its speed is not constant. With these conditions prevailing, its motion through time could be charted by placing a carbon stylus on its moving head, then pulling a strip of paper beneath it at a uniform rate. The reed’s displacement to-and-fro diminishes in a smooth fashion as time passes (decreasing intensity). Each cycle of its arc is equally spaced (uniform frequency). Each period of the motion forms the same arc pattern (uniform wave content). If this vibratory motion were audible, it could be described as follows: it grows weaker from the beginning (diminishing loudness) until it becomes inaudible; it remains at a stable level of highness (steady pitch); and it is of unvarying tonal quality (uniform timbre). If the reed were a part of a clarinet and the player continued blowing it with unvaried pressure, loudness, pitch, and timbre would appear as constants.

Pipe organs of the kind commonly encountered in Christian churches since the late Middle Ages are among the largest, most complicated, and most expensive musical instruments; they are products of sophisticated craftsmanship blended with artistry.
Reed organs and melodeon, types developed and mass-produced during the 19th century, are simpler and cheaper to construct than pipe organs.

Reed organany keyboard instrument sounded by vibration of metal reeds under wind pressure. “Reed organ” commonly refers to instruments having free reeds (vibrating through a slot with close tolerance) and no pipes.
Such instruments include the harmonium and the melodeon,  and are distinct from organs proper, i.e., pipe organs.  A type of small pipe organ describable as a reed organ is the regal, which has beating reeds (vibrating against a frame) and pipe resonators.

[Peter Anderson]

Part 2


Another well known, reed organ, was the foot-pumped harmonium.

Harmonium, also called Reed Organ, is a free-reed keyboard instrument that produces sound when wind sent by foot-operated bellows through a pressure-equalizing air reservoir causes metal reeds screwed over slots in metal frames to vibrate through the frames with close tolerance. There are no pipes; pitch is determined by the size of the reed. Separate sets of reeds provide different tone colours, the quality of the sound being determined by the characteristic size and shape of the tone chamber surrounding each reed of a given set; constricted chambers, for instance, induce powerful vibration and incisive tone. Volume is controlled by a knee-operated air valve or directly from the bellows pedals by an expression stop that allows the wind supply to bypass the reservoir. The instrument’s compass is normally four to five octaves.
The earliest instrument of the harmonium group was the physharmonica, invented in 1818 by Anton Haeckl in Vienna. His invention was inspired by the Chinese mouth organ, or sheng, which, taken to Russia in the 1770s, had introduced the free reed to Europe and aroused the interest of certain physicists and musicians. Now extinct, other types (such as John Green’s seraphine) appeared before Alexandre Debain produced his harmonium in Paris in 1840. The main improvements after 1850 were made by Victor Mustel in Paris and Jacob Estey in the United States.
The harmonium was a popular church and household instrument until the electronic organ drove it from the market after the 1930s. Compositions for the instrument include numerous works by the French composers César Franck and Louis Vierne and a quartet for two violins, cello, and harmonium by the Bohemian composer Antonín Dvořák.

They were widely used domestically and in small churches before becoming virtually obsolete by the mid-20th century, when electronic substitutes became commercially available. These electronic substitutes are versatile and relatively compact, though not necessarily inexpensive, and are chiefly useful in situations where tonal beauty, sensitivity, and imposing visual presence are not essential—for example, in popular music ensembles or homes. For more demanding purposes, electronic organs have given way in the late 20th century to even more versatile and portable synthesizers, which are also normally classified as electronic instruments.

Electronic instrument, any musical instrument that produces or modifies sounds by electric, and usually electronic, means. The electronic element in such music is determined by the composer, and the sounds themselves are made or changed electronically. Instruments such as the electric guitar that generate sound by acoustic or mechanical means but that amplify the sound electrically or electronically are also considered electronic instruments. Their construction and resulting sound, however, are usually relatively similar to those of their nonelectronic counterparts.

[Peter Anderson]

Here is an addition to this board from me, that I ought to post in a different colour, but I haven't.

This was typical of the Reed Organ, or Harmonium, both of which tended to have rather gaudy cases, especially if they were to be used in churches.



You can clearly see the two foot pedals at the bottom and these were pumped so that when one was up the other was down.   Producing the air in this way, meant they were self-contained and needed no other external power.

The 'flaps' under the keyboard were operated by the player's knees to adjust the volume.

Also notice that most of them also featured a variety of 'stops' to give different 'registrations'.

I wonder how many of you have actually played one of these?


Here is an American advert for such a magnificent organ, which appeared in 1882.   
The specification makes very interesting reading.



Remember back in 1882 the only organ 'competition' was a very expensive Pipe Organ!

In Britain we had small foldable and very portable reed organs.   The pedals, which were mounted on the base plate, that bin turn hinged down so that the collapsible sides, supported the main 'box' with the workings and keyboard.  The pedals operated the bellows with webbing straps that connected the pedals to the bellows inside the box.    Quite an ingenious design, that worked very well.

Similar to this, but with bellows operated by hand and not feet is this harmonium, still in extensive use today, especially in India.    Obviously they come in different finishes and with slight variations.

I have seen and heard these played on my visit to Delhi back  in 2007.

The player sits on the floor, and operates the spring loaded bellows at the rear with their left hand, and plays the keyboard with their right.    Again they have a few 'stops' to provide different registrations.
They are mostly used in concert with other Indian instruments, though not exclusively.   They are very popular in Indian schools.

Some have the bellows hinged at the bottom, so they could be operated by switching which hand you bellowed, and which one you keyboarded, if you were left handed, I suppose.



Peter

[Ian and Bev Harrison]

Hi Peter,
Your information on organs is very interesting and informative.  One small omission is to say that the reed organs almost all worked on vacuum not wind pressure, and the pedals & associated bellows were creating suction not wind pressure.
Cheers
Ian

[Peter Anderson]

Thank you for this important piece of information.

Which of us should pass this back to Encyclopaedia Britannica Inc?

Peter

[Roger Mardon]

Correct me if I’m wrong, Ian, but I believe the American reed organ was generally operated by suction bellows whereas the less common English harmonium was operated by pressure bellows.

Roger

[Peter Anderson]

The following is from Wikipedia:-

 A mechanic who had worked in the factory of Alexandre in Paris emigrated to the United States and conceived the idea of a suction bellows, instead of the ordinary bellows that forced the air outward through the reeds. Beginning in 1885, the firm of Mason & Hamlin, of Boston made their instruments with the suction bellows, and this method of construction soon superseded all others in America.

Peter

[Peter Anderson]

Again from Wikipedia, more on the Harmonium.

Harmoniums reached the height of their popularity in the West in the late 19th and early 20th centuries. They were especially popular in small churches and chapels where a pipe organ would be too large or too expensive; in the funeral-in-absentia scene from Mark Twain's The Adventures of Tom Sawyer, the protagonist narrates that the church pryocured a "melodeum" (a conflation, likely intended by Twain for satirical effect, of the names "melodeon" and "harmonium") for the occasion. Harmoniums generally weigh less than similar sized pianos and are not as easily damaged in transport, thus they were also popular throughout the colonies of the European powers in this period not only because it was easier to ship the instrument out to where it was needed, but it was also easier to transport overland in areas where good-quality roads and railways may have been non-existent. An added attraction of the harmonium in tropical regions was that the instrument held its tune regardless of heat and humidity, unlike the piano. This "export" market was sufficiently lucrative for manufacturers to produce harmoniums with cases impregnated with chemicals to prevent woodworm and other damaging organisms found in the tropics.

At the peak of the instruments' Western popularity around 1900, a wide variety of styles of harmoniums were being produced. These ranged from simple models with plain cases and only four or five stops (if any at all), up to large instruments with ornate cases, up to a dozen stops and other mechanisms such as couplers. Expensive harmoniums were often built to resemble pipe organs, with ranks of fake pipes attached to the top of the instrument. Small numbers of harmoniums were built with two manuals (keyboards). Some were even built with pedal keyboards, which required the use of an assistant to run the bellows or, for some of the later models, an electrical pump. These larger instruments were mainly intended for home use, such as allowing organists to practise on an instrument on the scale of a pipe organ, but without the physical size or volume of such an instrument. For missionaries, chaplains in the armed forces, travelling evangelists, and the like, reed organs that folded up into a container the size of a very large suitcase or small trunk were made; these had a short keyboard and few stops, but they were more than adequate for keeping hymn singers more or less on pitch.

The invention of the electronic organ in the mid-1930s spelled the end of the harmonium's success in the West (although its popularity as a household instrument declined in the 1920s as musical tastes changed). The Hammond organ could imitate the tonal quality and range of a pipe organ whilst retaining the compact dimensions and cost-effectiveness of the harmonium as well as reducing maintenance needs and allowing a greater number of stops and other features. By this time, harmoniums had reached high levels of mechanical complexity, not only through the need to provide instruments with a greater tonal range, but also due to patent laws (especially in North America). It was common for manufacturers to patent the action mechanism used on their instruments, thus requiring any new manufacturer to develop their own version; as the number of manufacturers grew, this led to some instruments having hugely complex arrays of levers, cranks, rods and shafts, which made replacement with an electronic instrument even more attractive.

The last mass-producer of harmoniums in North America was the Estey company, which ceased manufacture in the mid-1950s; a couple of Italian companies continued into the 1970s. As the existing stock of instruments aged and spare parts became hard to find, more and more were either scrapped or sold. It was not uncommon for harmoniums to be "modernised" by having electric blowers fitted, often very unsympathetically. The majority of Western harmoniums today are in the hands of enthusiasts, though the instrument remains popular in South Asia.

Peter

[Peter Anderson]

Part 3

The enormous and varied pipe organ repertoire is especially rich in solo music intended for performance in churches, either during the liturgy or before and after services. The organ’s most familiar ensemble role is accompanying choral and congregational singing, a function in which the organist may also conduct the singers. Organ recitals, a favourite form of public entertainment before the advent of radio and recordings, most often take place in churches but also occur in municipal auditoriums, concert halls, and other secular buildings where organs have been installed.
Perhaps most important among such venues in the early 20th century were theatres where organs were used to accompany silent films. Theatre organs, while not generally very large, were highly innovative in tonal and mechanical design and made use of technological improvements that were slow to find their way into more conservative church organs. Among the special effects produced by theatre organs are colourful sounds made by percussion devices that act independently from the pipes.

Parts, mechanism, and production of sound

Conventional pipe organs consist of four main parts:
     1     the keyboard or keyboards and other controls that collectively are called the console,
     2     the pipes that produce the tone,
     3     the mechanism, or action, and
     4     the wind generator.

Ideally, the pipes, action, and supporting framework are encased in a free-standing structure, or case, that protects the delicate interior parts and blends and projects the sound through generous openings into the surrounding space. Traditionally, rows of dummy or real pipes and carved woodwork in attractive arrangements partially screen the openings in the case. Because organ pipes are not uncommonly up to 32 feet long, organ cases can be very large and form a significant architectural component of the space.

The proper placement of an organ is acoustically crucial, and for most organ music a resonant room with three seconds or more of reverberation time is desirable. Organs having pipes that are installed in deep chambers adjoining the room occupied by the listeners, or placed in an acoustically “dead” environment, are likely to lack musical vitality. Fully exposed pipes without encasement, seen in many mid-20th-century organs, may produce a raw, unfocused sound.

[Peter Anderson]

Part 4

The simplest type of organ has one keyboard, or manual, and one pipe to each key. The pipes, supported vertically by a rack, stand in a row, or rank, on an airtight chest that is supplied with wind from bellows or a rotary blower. While rotary blowers driven by electric motors are highly efficient and tireless, the turbulence and inflexible pressure of their air flow can adversely affect the tone of the pipes. Many organ builders and players, especially of smaller instruments, therefore prefer hand-pumped bellows, which are responsive to musical demands if close coordination exists between the player and the pumper.

Under each pipe is a valve, or pallet, connected by a system of cranks and levers to its respective key. A reservoir, loaded by weights or springs to maintain sufficient wind pressure, is ordinarily interposed between the wind generator and the wind-chest. This reservoir has a safety valve that operates to relieve excessive pressure when the reservoir becomes full.
The pitch of each note is determined by the length of its pipe; the longest pipe emits the deepest note, the shortest pipe the highest note. If two comparable pipes sound an octave apart, the effective length of the higher-pitched pipe is exactly half that of the lower-pitched.
Since the tone of a pipe sounding on a constant pressure of wind is immutable, both as to quality and loudness, the expressive potential of an organ with only one pipe to each key is limited. All but the smallest portable organs, therefore, have at least three ranks, or sets, of pipes, and large church and auditorium organs may have 100 or more ranks. The pallet controlled from each key admits wind to all the pipes belonging to that key; but, in order that the organist may be able to use any of the ranks of pipes, alone or in combination, an intermediate mechanism is provided by which he may stop off any rank or ranks.

Stop, in music, on the organ, mechanism controlling the entry of air from the pressurized wind chest into a rank of pipes producing a distinctive tone colour. The word stop also denotes, by extension, the register, or rank of pipes, controlled by a stop. Stop also occasionally refers to mechanisms altering the tone colour of the strings of harpsichords and early pianos.
The earliest organ stops used a slider system. Holes in a strip of wood set in a slider frame coincided with holes in the feet of the pipes of one register. By pushing a knob the organist could slide the holes slightly beyond the pipe feet, blocking entry of air into those pipes. An alternate method was introduced in the 20th century, with electrically operated valves controlling entry of air into the pipes.
Each rank of pipes, such as the diapason, is controlled by a separate stop. Mutation stops consist of pipes sounding higher (e.g., by five notes) than the other pipes, rather than in unison with them. Used in combination with unison pipes they add an incisive quality to the sound. Mixture stops consist of two or more ranks of pipes, both unison and mutation ranks, controlled by a single stop.

From this function the control by whose operation the ranks are stopped off has come to be known in English as a stop, a term also used loosely for each rank of pipes.

[Peter Anderson]

Part 5

Stop and key mechanisms

The operative part of the stop mechanism lies between the pallet and the foot holes of the pipes. It normally consists of a strip of wood or plastic running the full length of each rank of pipes. In it is drilled a series of holes, one of which registers exactly with the foot hole of each pipe. The perforated strip, or slider, is placed in a close-fitting guide in which it may be moved longitudinally. When it is moved a short distance, so that its holes no longer register with the pipes, wind is cut off to that rank, even when the organist opens the pallets by means of the keys. Wind-chests in which the stops operate in this way are called slider chests. Other ways of working the stops will be referred to later; but the simple, reliable slider chest was in almost universal use before the 20th century. The slider is connected to the console by a system of levers and cranks, and it terminates in a knob that the organist pulls outward to bring the stop into play or pushes in to silence it. The name of the particular rank governed by the stop is usually engraved on the knob or appears on a label next to it. An organ’s tonal specifications are customarily defined by a list of the names of its ranks and their respective pitches.

Often the organist needs to play two or more interweaving, contrasted melodic lines, to give prominence to a melody against a quieter accompaniment, or to play loud and soft passages in rapid succession. None of these effects can be achieved on an organ with one manual, as so far described. For this reason, organs of more than about seven or eight stops usually have two manuals, each controlling its separate wind-chest and stops. Each manual department is self-contained, so that the organ is really a composite instrument. By prearranging the stops on the manuals, the organist may perform in any of the three ways mentioned above. The organist, therefore, may vary the sounds produced in one or both of two ways: by changing the stops on the manuals being played or by leaving the stops as they are and changing from one manual to another.

Since the 18th century organists have had yet a third way of controlling the volume of sound. The pipes of one or more manuals may be enclosed in a box, one side of which consists of hinged and movable shutters (similar to Venetian blinds) that are connected to a pedal at the console. By opening and closing the shutters, the sound from the stops of the manual concerned is made louder or softer. Such enclosures are called swell boxes. In pursuit of still greater expressivity, organists since the 16th century have often employed an accessory called a tremulant, which by repeatedly interrupting the flow of wind to the wind-chest creates a pulsation in the tone of the pipes.

Since the 14th century, one department of the organ has commonly been played from a keyboard controlled by the organist’s feet. The pedal department is basically like the manual departments but controls predominantly longer pipes. Modern organs normally have pedal keyboards of up to 32 notes.

The organist sometimes wishes to combine the stops of two different manuals or to couple one or more of the manuals to the pedals. This is effected by a simple mechanism, called a coupler, that is controlled at the console.

Certain combinations of stops on each manual are more commonly needed than others; in order that these combinations can be readily available, the console may be provided with several short pedals disposed above the pedal keyboard, or pedalboard. Each of these short pedals, called combination (or composition) pedals, is connected to one commonly needed combination of stops. When a combination pedal is depressed, the stops connected to it are drawn on, and any others that are already drawn are pushed off.

In the simplest mechanical action, the connection from key to pallet is by a series of cranks, rollers, and levers that transmit motion horizontally and vertically from keyboard to wind-chest. The overall distance may be considerable, and the main distance is bridged by trackers, slender strips of wood, metal, or plastic, which are kept in constant tension. Adjustment screws are employed to take up slack occasioned by wear and changes of humidity.

The mechanism of the organ as described so far is entirely mechanical, and such organs, including the great majority of those built before the late 19th century, are said to have tracker action. Tracker action is also used in many modern organs, especially those built according to historical principles.

[Peter Anderson]

Part 6

Tracker action, on the organ, is a mechanical system that transmits the organist’s action in depressing a key to the pallet valve that admits air into the pipes that the key controls. It consists of cranks, levers, and trackers, which are thin strips of wood connecting, under tension, parts of the organ action and conveying motion from one part to another.

On large organs with many stops and couplers, considerable manual strength is needed to operate the system and overcome wind pressure against the valve. In contrast to lighter 19th- and 20th-century pneumatic and electric actions, however, tracker action gives the player direct contact with the valve, resulting in a more sensitive touch. A revival of tracker action began in about 1925.

Many organists prefer tracker action to all other forms because it affords superior sensitivity of touch. Organs may, however, have pneumatic, direct electric, or electropneumatic action, although these actions result in a loss of sensitivity and responsiveness. In very large organs with tracker action, considerable strength may be necessary to depress the keys. Also, where the layout of the building is inconvenient and the departments of the organ have to be widely separated, tracker action is not practicable. To overcome these difficulties, especially with the object of lightening the touch, other forms of action were devised.

The first effective system was developed in the 1830s by Charles Spackman Barker, an Englishman. It consisted of a series of small, high-pressure pneumatic bellows or motors, one attached to each key of the main manual at the console.

Bellows - A mechanical contrivance for creating a jet of air, consisting usually of a hinged box with flexible sides, which expands to draw in air through an inward opening valve and contracts to expel the air through a nozzle. The bellows was invented in the European Middle Ages and was commonly used to speed combustion, as in a blacksmith’s or ironworker’s forge, or to operate reed or pipe organs.
In its simplest form, a hand bellows consists of two flat boards of rectangular, circular, or pear shape, hinged at one end and connected around their edges by a wide band of flexible leather to form an airtight joint. Wire rings keep the leather from collapsing when the boards are separated suddenly and the pressure in the chamber is less than atmospheric. One of the boards has a hole in the centre, covered inside by a leather flap or valve that can open only inward. The outlet nozzle has a relatively small opening.
When the boards are separated, the partial vacuum created causes the air to rush into the chamber through the valve; when the boards are brought together, the valve closes, and the air in the chamber is discharged through the open nozzle.

When a key was depressed, compressed air was admitted to the motor, which, in turn, operated the tracker action. Lacking encouragement at home, Barker went to France, where the great French builder Aristide Cavaillé-Coll employed the Barker lever almost exclusively from 1840 on.
Later, the trackers were supplanted by lead tubes, and the connection from key to pallet was solely by compressed air traveling through these tubes. This system was called tubular pneumatic action. At its best, it was remarkably effective, being reliable, long-lived, reasonably silent in action, and perfectly prompt in operation. At anything but its best, it was none of these things, and its worst fault usually lay in sluggish operation. Tubular pneumatic action is almost never used in modern times.

[Peter Anderson]

Part 7

As early as 1860, electric action was used experimentally, and it came into wide use at the end of the 19th century. Direct electric action, in which an electromagnet pulls the pallet open, is sometimes used, but a combination of electric and pneumatic mechanism is more general. In this system the depression of a key completes an electrical circuit, which energizes an electromagnet, allowing wind to enter a pneumatic motor attached to the wind-chest, and this motor opens the pallet. The stops may be operated in exactly the same way, but, where they are operated electrically, the sliders are often replaced by a series of valves, one to each pipe. The organ is then said to have a sliderless chest, and the most usual type is the pitman chest, so called because it contains a type of floating valve called a pitman. This action is commonly known as electropneumatic.

The combination pedals can also be operated electropneumatically. They are usually supplemented by a series of buttons, or pistons, placed below each manual, where they are conveniently operated by the organist’s thumbs. The pistons may easily be made adjustable so that the organist can quickly alter the combination of stops controlled by each one.

A compromise has been used successfully with tracker action for each department, with the coupler action operated electrically. This arrangement has considerable merit, since the coupling together of three or four manuals with tracker action results in a very heavy touch. Electric stop action may also be combined with tracker key action, enabling the use of electric (including solid-state) combinations—an invaluable aid in quickly changing groups of stops, especially in larger instruments.

[Peter Anderson]

Part 8

Flue pipes

There are two main categories of organ pipes: flue pipes and reed pipes. Flue pipes (made either of wood or metal; their construction is basically similar in principle) account for about four-fifths of the stops of an average organ. The photo below shows a front view and a vertical section of the most typical sort of metal flue pipe. The pipe consists of three main parts: the foot, the mouth, and the speaking length.


Typical flue pipe (principal).

The pipe stands vertically on the wind-chest, and wind enters at the foot hole. The foot is divided from the speaking length by the languid, a flat plate; the only airway connection between the foot and the speaking length is a narrow slit called the flue. The wind emerges through the flue and strikes the upper lip, producing an audible frequency, the pitch of which is determined by and amplified in resonance by the speaking length of the pipe. A pipe of this kind is, in fact, identical in principle with a recorder or a tin whistle; but, whereas they have holes along the speaking length, which the player covers and uncovers with his fingers to secure the notes of the musical scale, in an organ there is a separate pipe for each note.

The tone of a pipe is determined by many factors, including the pressure of the wind supply, the size of the foot hole, the width of the flue, the height and width of the mouth, and the scale, or the diameter of the pipe relative to its speaking length. The material of which the pipe is made also exerts an influence; it may be an alloy of lead and tin, wood, or, more rarely, pure tin or copper, and for the bass pipes zinc. The pipes may also vary in shape, a common variant being an upward taper in which the pipe is smaller in diameter at the top than at the mouth. Or, the top of the pipe may be completely closed by a stopper. Such a pipe is said to be stopped; a stopped pipe sounds an octave lower in pitch than an open pipe of the same speaking length.

Open pipes of large diameter are said to be of “large scale,” and open pipes of small diameter are said to be of “small scale.” Large-scale pipes produce a fluty or foundational quality of tone that is free from the higher harmonics (the numbered series of partials, or component tones). Small-scale pipes produce a bright quality of tone that is rich in harmonics, recalling bowed strings. Stopped pipes can be particularly foundational in tone, and they favour the odd-numbered at the expense of the even-numbered partials. Tapered pipes are somewhere between stopped and open pipes in tone quality.

Flue pipes are tuned by increasing or decreasing the speaking length. In the past, several methods of tuning were employed, but in modern times this is often done by fitting a cylindrical slide over the free end of the speaking length and sliding it up and down, lengthening or shortening the pipe as required. In stopped pipes the stopper is pushed farther down to sharpen the pitch or is pulled upward to lower it.
The pipe maker thus broadly fixes the type of tone that a pipe will produce; but this is further controlled within fairly wide limits by the wind pressure and, finally, by the voicer, who adjusts the tone of each pipe by manipulating the foot hole, flue, and upper and lower lips. The attack of the note may also be greatly influenced by cutting a series of small nicks in the edge of the languid. Heavy nicking, commonly practiced in the early 20th century, produces a smooth and sluggish attack. Light nicking or no nicking, as used up to the 18th century and in some more advanced modern organs, produces a vigorous attack, or chiff, somewhat like tonguing in a woodwind instrument. If not excessive, this chiff enhances the vitality and clarity of an organ. The voicer is the artist upon whom the ultimate success of any organ depends. The tonal designer or architect is hardly less important, however; it is he who decides upon the choice of stops, their disposition in the organ, and the scales to be followed by the pipe maker. A completely successful organ depends upon the effective cooperation of designer and voicer.

[Peter Anderson]

Part 9

Reed pipes

Organ reeds were probably originally copied from instrumental prototypes. A reed stop may have a beating reed like that of a clarinet or a free reed (a type discussed below in connection with reed organs).

The shallot of a beating reed pipe is roughly cylindrical in shape, with its lower end closed and the upper end open. A section of the wall of the cylinder is cut away and finished off to a flat surface. The slit, or shallot opening, thus formed is covered by a thin brass tongue that is fixed to the upper end of the shallot. The tongue is curved and normally only partially covers the shallot opening. But, when wind enters the boot, the pressure of the wind momentarily forces the tongue against the shallot, completely closing the opening. Immediately, the elasticity of the brass asserts itself, and the tongue reverts to its curved shape, thus uncovering the opening. This process is repeated rapidly. The frequency of the pulsations of air that enter the shallot is determined by the effective length of the reed and, in turn, determines the pitch of the note. Thence, the pulsations pass out into the tube, or resonator, which further stabilizes the pitch and decides the quality of the note. Most reed resonators have a flared shape. As in flue pipes, a wide scale favours a fundamental tone, and a narrow scale favours a bright tone. Cylindrical resonators produce an effect similar to that of stopped flue pipes, the note being an octave lower than the equivalent flared pipe and the tone favouring the odd partials. Some reed pipes, such as the vox humana, have very short resonators of quarter or eighth length. Pipes the resonators of which have no mathematical relationship to the pitch are known as regals; regal stops were popular in the 17th century, particularly with the North German school, and their use has been revived in modern times. Their short resonators have varying and peculiar shapes, which produce a highly characteristic snarling tone; they can be difficult to keep in tune.

Reed pipes are tuned by moving the tuning wire, thus shortening or lengthening the tongue. As in flue pipes, the scale and shape of the resonator largely determine the quality of tone to be produced; but the wind pressure, the shape and size of the shallot, and the thickness and curvature of the tongue also have important influence. The tongues may also be weighted with brass or felt; this weighting produces a smoother quality of tone, especially in the bass notes.