Organ pipe
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2008-06-11T02:47:00Z
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robot Adding: [[es:Tubo de órgano]]
[[Image:StRaphaelsDubOrganSmall.jpg|thumbnail|right|300px|The choir division of the organ at St. Raphael's Cathedral, [[Dubuque, Iowa]]. Wood and metal pipes of a variety of sizes are shown in this photograph.]]
An '''organ pipe''' is a sound-producing element of the [[pipe organ]] that [[resonator|resonates]] at a specific pitch when pressurized air (commonly referred to as ''wind'') is driven through it. Each pipe is tuned to a specific note of the [[musical scale]]. A set of organ pipes of similar [[timbre]] tuned to a scale is known as a ''rank'' or a ''[[Organ stop|stop]]''.
==Construction==
===Materials===
Organ pipes are generally made out of either [[metal]] or [[wood]]. Very rarely, [[glass]], [[porcelain]], [[plastic]], or even [[Rock (geology)|stone]] pipes may be seen.
====Metal====
Metal pipes are usually made of an [[alloy]] of [[lead]] and [[tin]], along with trace amounts of [[antimony]] and [[copper]] for increased rigidity. The percentage of each metal in the alloy depends on the desired characteristics of the resulting pipe. The more lead used in the alloy, the darker the resulting tone will be. Conversely, if a pipe has a high proportion of tin, it will have a brighter tone. In addition, high amounts of tin give a gleaming and long-lasting polish, which may be desired if the pipe is clearly visible. The cost of each metal is also a factor, as tin is more expensive than lead. The usual exceptions to tin-lead alloys are very lowest pipes in a rank, which are sometimes made of [[zinc]]. In addition, pipes have been made of many metals, including copper, [[aluminium]], [[gold]], [[silver]], [[brass]], and [[iron]].
Metal pipes are made by first [[casting]] a metal alloy of the desired metallurgical composition onto a long flat surface. Once the metal cools, it is cut into pieces, which are then rolled into shapes around molds called [[mandrel]]s and soldered together. Thus, the cross-section of a metal pipe is usually circular.
====Wood====
The body of a wooden pipe is made of either a coniferous wood or hardwood, although the lower section of the pipe (comprising the foot, cap, block and mouth) will nearly always be made from hardwood to provide a precise edge for the pipe's mouth. Using screws and glue, the pipes are assembled from wooden pieces of various shapes and sizes. In contrast with the circular cross-section of a metal pipe, the cross-section of a wooden pipe is most commonly square or rectangular.
===Shapes===
[[Image:Organ_pipe_types.png|thumb|Organ pipe shapes]]
The bodies of organ pipes are generally made in three shapes: cylindrical, conical, or rectangular. Cylindrical pipes are simple [[cylinder (geometry)|cylinders]], while conical pipes are in the shape of a tapering or expanding [[cone (geometry)|cone]]. Rectangular pipes form [[cuboid]] shapes with either a [[square (geometry)|square]] or [[rectangle|rectangular]] cross-section when viewed from above. There are some irregular shapes as well: the Flûte triangulaire, for example, has a [[triangle|triangular]] cross-section when viewed from above). In addition, a cylindrical or rectangular pipe can be ''tapered'': that is, it can be made to be wider at the bottom than at the top. The Internal shape of the pipe is a major factor in tone color.
The end of the pipe opposite the reed or mouth may be either open or closed (also known as ''stopped''). An open pipe produces a tone in which both the even-numbered and the odd-numbered [[Harmonic series (music)|partials]] are present, while a stopped pipe, such as a [[gedackt]], produces a tone with mostly odd-numbered partials. In addition, the wind travels both up and down the body of the pipe, doubling the length of the column of sound; thus, a [[Closed tube]] sounds an octave lower than an open pipe of the same length. The tone of a stopped pipe tends to be gentler and sweeter than that of an open pipe, though this is largely at the discretion of the voicer.
<!-- Stopped pipes are also used in situations in which there is limited space and/or money available, and a full-length rank of pipes (especially bass pipes of 16′ and 32′ length) would take up too much space and/or be too costly to build. It is quite common for the lowest few notes of an otherwise open rank of pipes to be stopped or folded ("U" shaped) for this reason. -->
==Pitch==
:''For more about the pitch of organ stops, see [[Organ stop#Pitch and length|Organ stop: Pitch and length]].''
The pitch produced by an organ pipe is a function of its length. The nomenclature of a rank of pipes, for example an "8 foot" Open diapason refers to the length of the longest pipe in the rank. Thus the longest pipe, C, (two octaves below [[middle C]]) is 8 feet long. This length represents approximately 1/2 of the frequency wavelength for an open Pipe. An 8ft stop sounds at unison pitch, like a [[piano]]. Much like a vibrating [[Strings (music)|string]], the [[frequency]] of the tone of an open pipe half the length of another, will sound one [[octave]] higher. If the longest pipe, C, is 8 feet in length, the pipe one octave higher will be 4ft long, and two octaves above (middle C) will be 2ft long. Closed or [[Gedackt]] pipes will represent frequency wavelengths approximately 4 times their length. Example: A Gedackt/closed C pipe (2 octaves below middle C) will be 4ft long.
==Varieties==
===Flue pipes===
{{main|Flue pipe}}
[[Image:Schuke-sofia-principal.JPG|thumb|right|250px|A set of flue pipes of a diapason rank in the Schuke organ in [[Sofia, Bulgaria]].]]
The sound of a flue pipe is produced with no moving parts, solely from the vibration of air, in the same manner as a [[recorder]] or a [[whistle]]. Wind from the "flue", or windway is driven over an open window and against a sharp lip called a ''Labium''. By [[Bernoulli's principle]] this produces a lower pressure region just below the window . When the [[vacuum]] under the window is large enough, the airstream is pulled under the Labium lip. Then the process works in reverse, with a low pressure region forming over the Labium which pulls the airstream to the other side again. This 'fluttering' airflow creates high and low pressure waves within the pipe's air column. A high and a low pressure wave form a single "cycle" of the pipe's tone. The oscillating airflow produced by the Labium is called a [[Von Karman vortex street]].
Flue pipes generally belong to one of three tonal families: ''flutes'', ''diapasons'' (or ''principals''), and ''strings''. The basic "foundation" (from the [[French language|French]] term ''fonds'') sound of an organ is composed of varying combinations of these three tonal groups, depending upon the particular organ and the [[organ literature|literature]] being played. <!-- About four-fifths of organ pipes are flue pipes.<ref>[http://www.madehow.com/Volume-5/Pipe-Organ.html How the organ is made]</ref> -->
The different sounds of these tonal families of pipes arise from their individual construction. The tone of a flue pipe is affected by the size and shape of the pipes as well as the material out of which it is made. A pipe with a wide diameter will tend to produce a flute tone, a pipe with a medium diameter a diapason tone, and a pipe with a narrow diameter a string tone. A large diameter pipe will favor the fundamental tone and restrict high frequency harmonics, while a narrower diameter favors the high harmonics and suppresses the fundamental. The science of measuring and deciding upon pipe diameters is referred to as ''[[organ flue pipe scaling|pipe scaling]]'', and the resulting measurements are referred to as the ''scale'' of the pipe. Ranks of all three tonal families can be either open or stopped, although flutes are by far the most common of the three to be stopped.
===Reed pipes===
{{main|Reed pipe}}
[[Image:Vox Humana rank taken in 2004.jpg|thumb|right|200px|A rank of Vox Humana (reed) pipes, with part of the reed section of the organ shown in the background.]]
The sound of a reed pipe is produced by a beating ''[[reed (music)|reed]]'': wind is directed towards a curved piece of [[brass]] (the reed). A partial vacuum is created by higher velocity air flowing under the Reed which causes it to be pulled closed against a hard surface called the ''shallot''. This shuts off the vacuum and allows the Reed to spring open again. A tuned [[resonator]] extends above this assembly and reinforces the sound produced. The principle is the same as that of the orchestral [[clarinet]]. The pitch of a reed pipe is determined primarily by the length of the reed but the cubic volume of air in the resonator supports that frequency. Most Reed pipes have a slide to adjust the vibrating length of the Reed to fine tune it. Because of the precision required in the making of the vibrating reed,resonator pipe and its accompanying parts, reed pipes are more complicated to manufacture than flue pipes.
By altering any of several parameters (including the shape and cubic volume of the resonator, as well as the thickness and shape of the reed), a reed pipe can produce a wide variety of tonal colors. This allows reed stops to imitate historical musical instruments, such as the [[crumhorn|krumhorn]] or the [[Regal (musical instrument)|regal]]. Because the resonator is partially stopped/closed by the Reed, odd-numbered partials/harmonics are dominant (in the hollow tones of Krumhorn and Clarinet stops, for example). If the resonator pipe expands outward to conical, the geometry allows the production of both even- and odd-numbered partials, resulting in the fuller tones of Trumpet and Oboe stops.
===Diaphone pipes===
[[Image:64' diaphone atlantic city.gif|thumb|right|350px|The 64' diaphone-dulzian pipes from the organ of Convention Hall, Atlantic City, New Jersey.]]
The '''diaphone''' is a unique and uncommon organ pipe. Invented by [[Robert Hope-Jones]] around [[1900]], it has characteristics of both flue pipes and reed pipes. The pipe speaks through a resonator, much like a reed pipe, but a spring-loaded ''pallet'' instigates the vibration instead of a reed. The pipe is generally made of wood and can be voiced at various wind pressures. The diaphone is usually found at 16′ and 32′ pitches, however there are a few examples of 8′ diaphones, and a full-length 64′ Diaphone-Dulzian is installed in the [[Boardwalk Hall Auditorium Organ]] in [[Atlantic City]]. <!--(which is one of only two full-length 64′ stops in the world, the other being the Contra Trombone stop in the organ at the [[Sydney Town Hall]] in [[Sydney, Australia]]). -->
Hope-Jones also developed an imitative version of the diaphone called the ''diaphonic horn'', which had a more reed-like quality than the diaphone and was voiced on lower wind pressures. [[Wurlitzer]] built a version of the diaphonic horn for their [[theater organ]]s at 32′ and 16′ pitches with huge wooden resonators as extensions of its Diaphonic diapason, and at 16′ with metal resonators as an extension of its smaller-scale Open diapason. The [[Austin Organs, Inc.|Austin Organ Company]] also developed a metal diaphone at 16′ pitch known as a Magnaton. Due to its penetrating tone, the diaphone has also been used in [[foghorn]]s and fire signals.
A working example of a Hope-Jones diaphonic horn survives at Battersea Arts Centre (formerly Town Hall) in the large HJ designed concert organ there. This stop is pitched at 8ft and extends as a diaphone up to about middle G, where its resonators are only about a foot long. After that it is of flue pipes. It also extends down to 16ft pitch, although the lower octave is not working at present. The Battersea organ is currently being restored and is likely to be the largest and most intact example of a Hope-Jones designed instrument left in the UK.
==References==
<references/>
[[Category:Pipe organ components]]
[[Category:Musical instrument parts and accessories]]
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