Instrument of ancient origin, consisting of a keyboard, wind supply, and pipes tuned to different pitches, along with a mechanism linking the keyboard to
shunts that direct air from the wind supply to specific pipes, allowing them to sound. Ctesibius of Alexandria, an engineer of the third century B.C., is credited with the invention of the earliest known pipe organ, the hydraulos, in which water pressure was used to regulate the flow of air to the pipes. Instruments of this type were difficult to construct and maintain, and later designs utilized bellows compressed by the weight of men or boys standing on or pumping them. During the early Middle Ages, Constantinople became a center of organ building; in 757, at the request of Pepin the Short (the father of Charlemagne), Constantine VI, the Byzantine emperor, sent a large organ to France, along with an assembly crew and an organist trained in Constantinople. This was the first documented organ in Western Europe. Charlemagne received a second instrument, fitted with bronze pipes and leather bellows, at Aachen in 812. Around 900, organs began to come into use in churches. The “keys” on early medieval organs were really levers and were most likely hand-operated, but by the end of the 13th century an arrangement resembling the modern keyboard, with broad finger-operated keys, had been introduced.

The pipe organ in Saint-Germain l'Auxerrois, Paris

During the 14th and 15th centuries the art of organ building advanced gradually on many fronts, the general trend being toward larger instruments with greater numbers of pipes and an increasing variety of stops (ranks of pipes that have a specific sonic character or timbre). By 1500, a typical large northern European organ had two or three manuals (keyboards), as many as 15 different stops, a pedalboard capable of engaging several stops, and between 750 and 1,000 pipes. Innovation accelerated during the early years of the 16th century: new stops imitating the sounds of various flutes, brass, and reed instruments were added, and the organ’s palette was further enriched by the increasingly common deployment of mixtures (stops combining two or more ranks of pipes that “harmonize” above a given note, usually by reinforcing the octave, fifth, or third, sometimes by highlighting one of the weaker overtones). The process of aggrandizement and refinement (both mechanical and tonal) continued through the 17th century, on a trajectory that reached its apogee in the works of the German Baroque builders Arp Schnitger (1648-1719) and Andreas (1678-1734) and Gottfried (1683-1753) Silbermann. The younger Silbermann’s instruments in particular synthesized the best of the French and German traditions; magnificent achievements, they possessed the power, clarity, and brilliance to delineate the polyphonic textures of two distinctively complex forms of the era, the passacaglia and the fugue. Subsequent 18th-century builders were able to match the power of the best early-18th-century organs, but not always their “rationality,” their balance, and the beauty of their sound.

Modern replica of the Aquincum hydraulis from 228 AD

The next major developments in organ design and construction came via the efforts of the French builder Aristide Cavaille-Coll (1811-99). After winning the competition to build the new organ for the basilica of St. Denis in Paris in 1833, the young Cavaille-Coll made the first practical use of a pneumatic assist that overcame the hardness of touch common on large organs. This important change in the instrument’s action led to the development of the so-called “symphonic style” organs of the later part of the century. Cavaille-Coll went on to build many fine instruments in Paris, including those at Notre Dame, St. Sulpice, and St. Clothilde, as well as organs in Sheffield and at the Royal Albert Hall in London.

By the beginning of the 20th century, the electrification of mechanical parts of the organ led to the creation of instruments of monstrous power and size that found homes outside the church. The innovative builders who developed the modern theater organ included Henry Willis, Robert Hopejones, and the American Ernest M. Skinner. At the other end of the spectrum from these behemoths, as a response to the 20th-century revival of Baroque performance practice, interest focused on rediscovering the secrets of the pipework and mechanics of 17th- and 18th-century organs. Brilliant, clear, and versatile instruments have been produced along these lines by the firms of C. B. Fisk,Walter Holtkamp, and G. Donald Harrison of the United States, by Walcker, Steinmeyer, Klais, and Kemper in Germany, by the Dutch firm of Flentrop, and by Marcussen and Frobenius in Denmark.

The organ was originally regarded as a foundation instrument, its main purpose to support voices or accompany other instruments during church services. As the practice of preluding grew more popular, the solo capabilities of the organ captured the interest of many of the great keyboard composers of the 16th and 17th centuries— John Bull (ca. 1562-1628), Sweelinck, Louis Couperin (1626-61), Pachelbel, Fresco-baldi, Louis-Claude Daquin (1694-1772), Handel, and J. S. Bach. The greatest master of organ music in the late 17th century was the Danish-born Dietrich Buxtehude, organist at the Marienkirche in Liibeck from 1668 to his death in 1707. He was also the single greatest influence on Bach, whose contributions to the literature (among them the Passacaglia and Fugue in C minor) are unsurpassed. With the emergence of the galant style, the organ lost favor with composers. Mozart wrote a small number of church sonatas calling for organ accompaniment, and a handful of pieces for “mechanical” organ; Beethoven wrote nothing for the instrument. The next composer of importance to the repertoire was Mendelssohn, a fine organist whose most significant contributions were his Six Sonatas, Op. 65, and Three Preludes and Fugues, Op. 37. Brahms penned the Fugue in A-flat minor (1856) and a set of 11 chorale preludes (1896), while Liszt made numerous arrangements for organ of pieces by other composers, and composed some impressive original works. Other notable contributions from German Romantic composers were made by Julius Reubke (1834-58), Joseph Reinberger (1839-1901), and Reger, who wrote many highly chromatic and densely textured works.

Baroque pipe organ of the 18th century at 
Monastery of Santa Cruz, Coimbra, Portugal

During the second half of the 19th century, some of France’s best composers found positions (and a measure of financial security) as organists in Parisian churches. At the Church of la Madeleine, Camille Saint-Saens presided over the organ from 1857 to 1877, followed by Theodore Dubois (1837-1924) and Gabriel Faure; at St. Clothilde, Cesar Franck was the incumbent from 1858 until his death in 1890; at St. Jean-St. Francois, Leo Delibes from 1861 until 1872; and at St. Sulpice, Charles-Marie Widor (1844-1937) played from 1870 until 1934, an astonishing tenure of 64 years. The chief successors to this generation included Maurice Durufle, Jehan Alain (1911-40), and Olivier Messiaen, who
was appointed organist at La Trinite in 1930 and continued to play there until shortly before his death in 1992. Of all the brilliant creations by the French organist-composers of the 19th and 20th centuries— whose number also includes Alexandre Guilmant (1837-1911), Louis Vierne (1870-1937), Marcel Dupre (1886-1971), and Jean Roger-Ducasse (1873-1954)— the works of Franck, Widor, Messiaen, and Alain are the most significant.

As the 21st century begins, innovations to the organ are still being made, the most significant and controversial of which is the incorporation of electronically produced tones. While synthesized sound is embraced by many, champions of authentic performance practice favor historically faithful sound and construction. Above all, organs continue to evolve in response to the specific needs and limitations of their venues.

The Cavaillé-Coll organ of the cathedral of Nancy (France)


An organ may be said to consist of two basic types of components: tonal and mechanical. The tonal portion comprises the pipework and the manner in which it is laid out, scaled, voiced, and tuned. The mechanical portion consists of the wind-chests on which the pipes stand, the key and stop actions connecting the console (or keyboard) to the wind-chests, and the bellows, regulators, and other components of the wind supply.


1. Pipework.
Organ pipes are made of various metals or of wood. The commonest pipe material is composed of lead and varying quantities of tin, plus small amounts of stabilizing metals, such as antimony. Metal with 30 percent tin is called common metal; metal with 50 percent tin, spotted metal, due to its characteristic appearance. Nearly pure tin, because of its bright appearance, is sometimes used for facade pipes, and also for interior pipes, particularly those of the principal and string families, although flute-toned pipes are usually of common metal. Other metals used in pipes include copper (for reed resonators and decorative facade pipes) and zinc (for painted facade pipes and large bass pipes). Wooden pipes, rectangular in cross section, may be made of pine, fir, poplar, or hardwoods such as oak. Pipe materials have a subtle effect on sound quality, and thus certain materials are preferred for particular stops.


Organ pipes fall into two general classes, depending on how their sound is generated. Flue pipes sound on the same principle as a penny whistle or recorder. Wind, admitted through the toe hole in the foot of the pipe, passes through the flue (an opening between the languid and lower lip), striking the upper lip and setting in vibration a column of air in the body of the pipe [see Fig. 1], A pipe that is stopped (closed at the top) sounds an octave lower than an open pipe of the same length, because of the doubling back of the standing wave. Flue pipes (Principals, Flutes, Strings) represent the majority of stops in an organ and contribute a wide range of dynamics and timbres, depending on their scaling, voicing, and material.

Reed pipes sound on the same principle as a clarinet and supply voices of great variety and often brilliance. Their sound is generated by a thin metal tongue, acting as a reed, which vibrates against the open side of a metal or wood shallot (much like a clarinet mouthpiece) when air is forced into the wind-tight housing (boot) surrounding the reed assembly. Reed pipe resonators largely determine tone quality. They may be full length, half length, or fractional length, of flared or cylindrical form, open or partly closed at the top.

The pitch of an organ stop is indicated by the speaking length (in feet) of its longest pipe, not including its foot. Therefore a Principal 8' (the basic unison stop) has a bottom C pipe eight feet long. Pipe lengths halve at each octave; thus a 4' stop sounds an octave above an 8' stop, a 2' stop two octaves above, and a 16' stop an octave below. The same system applies to stops sounding intervals other than octaves: 5 1/3' produces the fifth, 2 2/3' the twelfth, 1 3/5' the seventeenth, and so on. These off-unison pitches enrich the harmonic series and are often referred to as mutations. For stopped pipes, the sounding pitch for C is used, although the actual length of the C pipe at 8' C is only 4'. In reed pipes, pitch is determined by a combination of resonator length and vibrating length of the reed tongue; sounding pitch at C is always designated, even though some reed stops (such as Regals) may have resonators as little as one-fourth of the designated length at bottom C.

Scaling refers to the relation between the diameter and the length of a pipe, and this in turn determines its tone “family.” Scales for all stops in a given organ must be carefully planned if good ensemble and blend are to result. Among flue pipes, Principals (which, at various pitches, form the essential chorus of the organ) are of medium scale. Flutes have a wider scale, which suppresses harmonics and gives a more fundamental tone, and Strings have a narrower scale, which suppresses the fundamental and encourages more harmonic development.

Principals are always open pipes, usually of metal but in rare cases of wood. They range from the narrower and more harmonically developed Geigen (or Violin) Principal to the fuller-sounding Open Diapason. Strings (Salicional, Gamba, Aeoline) are always open metal pipes, usually rather softly voiced. The Flute family has the greatest variety of construction and tone color. Stopped Flutes (Stopped Diapason, Gedeckt, Bourdon) can be of either wood or metal and have a fairly foundational tone with a slight fifth harmonic. Half-stopped Flutes (Chimney Fute, Rohr-flote) have a small “chimney” instead of a stopper, can be of wood or metal, and have a brighter harmonic color. Tapered flutes (Spitzflote, Spillflute) are wide at the mouth and narrower at the top and usually fairly foundational, although a more narrow-scaled stop of this type, the Gemshom, has more harmonic development and functions as a kind of hybrid color. Open flutes (the metal Night Horn or wood Melodia or Clarabella) are usually of fairly wide scale and foundational tone; a variant is the Harmonic Flute, which is double-length in the treble and produces a very pure flute tone. Scaling in reed pipes relates to the resonators, wider resonators (especially when tapered) producing a fuller and more foundational tone than narrow ones.

Voicing is the regulation of each pipe’s tone quality, loudness, and promptness of speech, a demanding and time-consuming operation. Voicing is begun at the workbench and completed (finishing) where the organ is to be heard, to ensure proper balance among all the stops. For flue pipes, critical voicing factors include the sizes of the toe hole and flue opening, the position of upper and lower lips, the precise contour and position of the languid, and the distance (cut-up) between upper and lower lips. For reed pipes, the thickness and degree of curvature of the reed tongue are the voicer’s most important concerns.

The tuning of open flue pipes is accomplished by slightly increasing or decreasing the resonating length of the pipe, by adjusting a tuning slide or a slot in the back of the pipe, or by using a metal cone to increase or decrease the opening at the top. Stopped flue pipes are tuned by moving their stoppers or caps, reed pipes by moving a spring wire that bears against the reed tongue or by adjusting a slot near the top of the resonator.

2. Wind supply and wind-chests.
Wind pressure affects the loudness and tone quality of an organ. It is held approximately constant by weights or springs on the bellows and is normally determined in accordance with the size and acoustical properties of the space and the tone quality desired. The traditional wind supply consists of a pair or more of wedge-shaped bellows, raised by hand and collapsed in sequence by their weighted tops, the wind reaching the wind-chest through rectangular wooden ducts. Miniature versions of this system may be seen protruding from the side or back of portative organs.


By the late 18th century, single or multifold reservoirs were interposed, located as close as possible to the wind-chests. Other changes made by 19th-century builders included the development of tiered reservoirs capable of supplying different pressure for different stops (especially reed registers) or for treble and bass of the same stop. Because of the influence of historical styles on late 20th- and early 21st-century organ building, any of these types of wind supply may be found in contemporary organs.

Wind-chests of various types were designed during the organ’s long history, but by the mid-17th century, the slider chest emerged as the norm. This consists of a rectangular wooden box filled with wind, with the pipes located on its top in rows roughly parallel to the keyboards. A thin wooden strip or slider runs from left to right underneath the pipes of each row or stop. The slider has one hole for each pipe and can be positioned so that the slider holes either are or are not in line with the pipe holes above them. All the pipes for each note stand over a single wind channel or groove (perpendicular to the keyboard), to which air is admitted by a pallet valve connected to the key. By moving the sliders, the player determines which pipes receive wind from their wind channel and thus whether one or more stops will be heard.

3. Key and stop actions.
All organs have two distinct actions, one connecting the keys to valves under the pipes, and another to control the stops. Traditional key action employs a direct mechanical connection (by means of a thin wooden tracker, hence tracker action) between each key and the corresponding pallet valve in the wind-chest [see Fig. 2], The stop action consists of strong wooden connections from the sliders to knobs located near the player, who may place each slider in the on or off position by moving the knob. When the key is depressed, the valve opens, admitting wind to the wind channel for that note and to the pipes with which slider holes are aligned, i.e., to pipes belonging to the stops that have been drawn. Because all the pipes for any note receive their wind from the same note channel, an important blending of combined sounds is achieved.

Various modifications of the traditional actions were tried during the 19th century involving pneumatic means for operating key valves and sliders, most notably the pneumatic lever (Barker machine) first used by Cavaille-Coll of Paris and soon adopted by builders in other countries for larger organs built during the second half of the 19th century. The introduction of electricity around the turn of the century led to replacement of the traditional actions by either direct electromagnetic valves or a combination of magnets and pneumatic motors. This allowed keyboards to be separated from wind-chests, since no mechanical linkage was required but only an electric cable. For most American builders, the pitman electropneumatic wind-chest became the standard, along with adjustable combination actions controlled by thumb pistons underneath the keyboards. These systems accounted for practically all the organs built in the U.S. from the early 20th century through the 1960s.

During the second half of the 20th century there was a renewal of interest among both organists and builders in the traditional all-mechanical type of key action. The study of historic organs and a desire for a more touch-sensitive action were factors in this, and an increasing number of organs have been built with slider chests and tracker key action. In smaller instruments, stop action has also been mechanical, but in larger organs it is not uncommon to find electrically controlled stop and combination actions, and sometimes Barker machine key or coupler actions. An organ built in the early 21st century may thus have either mechanical or electrically controlled action, or a combination of both types.

4.    Organ case.
The late 20th century also saw a revival of the traditional organ case, which involves placing the pipes for each division in a separate, shallow, wooden enclosure, open at the front, with keyboards located in the center of the main case. Traditional practice places the pipes for the main Principal stop for each division in the facade of its case, suggesting the size and resources of the organ and filtering out the less desirable high-frequency content of organ pipe sound.


Architecturally, the case restores to the organ an identity that had been lost, at least in the U.S., where many instruments were built into recessed spaces whose facades gave no hint of the often extensive instruments behind them. Well-designed and ornamented cases for the Great, Positive, and Pedal divisions, for instance, announce visually the nature of the instrument in relation to the space where it is heard. Acoustically, organ cases project and blend the sound of each division. Free-standing cases, located near reflecting walls and ceiling, provide maximum reinforcement of sound.

Swell boxes, which consist of enclosures with louvered shutters at the front, are usually installed in the main case. Opening and closing the shutters controls the loudness and harmonic development of the pipes contained within the enclosure. Swell divisions became important in 18th-century English organs and from the 19th century in France, although they were not a part of classical designs in France or northern Europe.

J. S. Bach - Toccata and Fugue in D minor BWV 565

Jan van Eyck.  The Ghent Altarpiece.  Angels Playing Music

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