The wind turbine , also called bellows , wind turbine or simply called "blower" in modern organs , is an assembly of the organ that is responsible for the uniform generation, regulation, distribution and modeling of compressed air , which is called wind in organ building and barrel organ building .
Today the winch usually consists of a centrifugal fan (wind generation), a magazine bellows (regulation) and wind tunnels (distribution), which direct the wind to the wind chests on which the organ pipes stand. Often there is also a tremulant as wind modulation in the wind turbine.
The wind pressure depends on the design and characteristics of the built-in registers, on the acoustic properties of the room and on the desired overall sound of the organ. The pressure of the organ wind is measured in millimeters of water using a so-called wind balance (1 mm water column = 9.807 Pa ), which used to consist of a curved glass tube (also called a snake tube) filled with water. Starting with a wind pressure of around 50 mm water column in early baroque Italian and southern German organs, this rose to 100 mm water column in the High Romantic period. Particularly sharp-sounding so-called high pressure registers with a wind pressure of up to 300 mm water column as a rule were also built during this time . For open-air organs, such as the Heldenorgel in Kufstein, a wind pressure of 470 mm water column is required. With the Vox Maris , the loudest organ in the world according to the Guinness Book of Records , a wind pressure of 100,000 mm water column (around 10 bar) is required as an extreme exception. This high pressure is no longer generated by a centrifugal fan, but by a compressed air system.
In most modern organs, the wind is generated by radial fans , which use rotating paddle wheels in a housing to compress the air and release it continuously. Although this wind is slightly restless due to turbulence, it is nevertheless so constant that only smaller swimming bellows are required in order to achieve the desired uniform wind flow while playing. Most centrifugal fans work in a speed range from 1500 to 2500 rpm. The slower the fan runs, the less turbulence and flow noise the wind it generates. On the other hand, high-speed fans are more compact in their design and thus save space and are more cost-effective. The location of the centrifugal blowers should be such that, if possible, no direct or indirect motor noises can be heard. In principle, centrifugal blowers should therefore be set up vibration-free in order to prevent the transmission of structure-borne noise to the surface of the motor and to the other wind turbine. The transmission of direct engine noises through airborne noise is prevented with large centrifugal blowers by setting them up in a separate room, with smaller blowers by placing them in a sound-insulated box inside, with positive and small organs sometimes also outside the organ case .
Historical outline with technical and performance-related importance
Before the era of electrification, up to the end of the 19th century, helpers called Kalkanten or bellows treaders had to operate so-called scoop bellows to generate the play wind. These were mostly as Keilbalg or as wrinkle realized or Kastenbalg and were to be operated with the hands or feet. Depending on the size of the organ, up to twelve calcants were required, which had to be constantly on standby and started their work when required. As a signal, the organist operated a stop which was connected to a little bell.
A play wind generated with muscle power is rarely used in today's practice. Even with historical organs, the lime is replaced or at least supplemented by electric fans. Nevertheless, a naturally generated wind at concerts and recordings from old organs and in the area of historical performance practice is valued: the play wind, which is usually generated by several wedge bellows, is emitted extremely calmly and evenly to the instrument. Depending on the skill of the calculator, tiny fluctuations are only occasionally audible when changing the bellows. After the bellows has been pulled up quickly by lifting the bellows plate on the upper side and loaded with weights on one side (by hand or, in the case of large bellows, using a mechanically deflected footstep), it must then be released carefully so as not to cause any audible gusts of wind. Small irregularities resulting from this process are perceived by the player and listener as a "living wind". Such an organ wind is basically free of any kind of interference from vibrations or turbulence noises from a rotating paddle wheel, the frequencies of which are within the audible range. Indirect engine noises that are transmitted through the organ case are also absent. In the case of new buildings in a premodern organ style, bellows that correspond historically to the respective type of instrument are increasingly being used. When restoring premodern instruments, the focus is on the preservation of the original wind turbine, so that even on special occasions, a wind generated manually by lime edges can still be used. Often attempts are made to utilize the advantages of the bellows by adding mechanical, pneumatic or electrical inflation or elevator systems. However, the susceptibility to errors, the operating costs due to maintenance and wear and tear used to be very high. Successful technical implementations of more recent date are the bellows elevator machines with geared motors, such as the Dummel organ restored in 2007 in St. Leonhard ob Tamsweg or the so-called pumping bellows system in the Ignaz Egedacher organ restored in Vornbach in 2009 .
For older music, the liveliness and calm of the organ wind achieved in this way - often described as "breathing" of the organ - is valued, whereas for music since the late 19th century, absolute wind stability was required. To achieve this goal, the construction of the bellows has also been completely changed. One or more bellows convey air into a magazine bellows, which serves as a reservoir. The rhythm of the air to be drawn was no longer determined by the lowering of the respective bellows. The goal of the Kalkanten was to achieve the maximum possible expansion of the magazine bellows and then to maintain this during the game, which could be read off a pointer device near the pedal system. Small bellows, which were installed in several areas of the organ, cushioned even the smallest bumps in the play wind. This changed the requirements for the lime edge. After a short briefing, anyone could draw wind, which also led to a lot of anecdotes about "bellows kicking". Many people had direct contact with organs in this way. Attempts to make human strength superfluous with water and steam energy often failed. Gas engines from the late 19th century brought their first successes . Only with the triumphant advance of electricity was the organist able to make organ sounds heard at any time.
An even organ wind is essential for an organ to function. The organ wind has a great influence on the pitch and character of the sound of an organ. Organs equipped with centrifugal fans hardly need large bellows to regulate the organ wind. Float bellows are now usually made much smaller and are either located directly on the wind chest or even on the underside of the wind chest itself as a loading bellows . They serve almost exclusively to compensate for fluctuations in air pressure that arise from the slight turbulence in the engine and that are generated by playing at the pulpit .
Since a simple shut-off (throttling) is sufficient to regulate the wind flow to the bellows, so-called curtain or roller valves are also used in addition to other types of valves such as simple disc valves or sliders.
The effect of unintentional fluctuations in wind pressure when playing the organ is called gust of wind. Side effects of the gust of wind are audible fluctuations in pitch up to the failure of individual whistles (dependent on a stable wind supply) such as reed whistles . This phenomenon occurs mainly in historical organs from the Baroque era (and their replicas). Wind gusts are largely unknown in romantic organs. The gust of wind led to the fact that in the 1960s and 1970s the so-called “equality doubling ban” was taught - when registering Baroque literature, no two registers of a footnote number should be used at the same time. From today's point of view and taking historical sources into account, this view is to be regarded as outdated.
The aim of all the constructions listed so far is to guide the organ wind to the organ pipes as free of fluctuations and jolts as possible. With the help of a tremulant , periodic pressure fluctuations can be generated. This creates a vibration of the tones of the entire part of the work or, depending on the construction, often with small organs, of the entire instrument. With some modern tremulants it is also possible to adjust the speed of the vibrations to be generated. The setting can be made on a controller that is located on the console. There are also tremulants for a single register .
The wind throttle is an organ building technology of the 20th century. The organ wind is brought below the level of the specified target pressure. The organist can achieve completely different sound effects more or less randomly by means of a stepless control. Technically, this device is usually implemented by electronic modulation of the rotational speed of the organ motor. This special sound variant is required for some organ works by György Ligeti , for example .
The wind passes through mostly wooden wind tunnels from the fan through various bellows systems to the wind chests . The wind tunnels must be built in such a way that they guide the wind to the destination with as little pressure loss as possible and without major turbulence. Care must also be taken to ensure that no outwardly penetrating flow noises arise in them . The same applies to the valve boxes and chambers on the wind chest itself. Sufficient dimensioning of the wind tunnels has an influence on the quality of the organ sound that should not be underestimated.
In organs with pneumatic game - or key action the winch is also responsible for the generation of the so-called working wind, with pneumatic actions is responsible for valve control. The opposite is the play wind, which is intended for the sound generation in the pipes. It makes sense to design the working wind with a higher pressure than the play wind, as the control works faster and more precisely. However, this means a much more complicated and expensive construction of the fan or bellows system. Therefore, in practice, the pressure of the working wind is usually identical to that of the play wind.
In addition to supplying pipes, the organ wind was used primarily in the Renaissance and Baroque periods to drive other effect registers such as cymbal stars , which can now also be driven electrically.
In the case of portatives , a multi-bellows that can be pulled out wide is attached to the rear of the instrument without weights. In addition to operating the keyboard with the right hand, the player is also responsible for meaningful and even air flow, which is performed by the left hand. In return, the hand-held bellows allows you to vary the mood, sound and volume of the pipes by directly influencing the wind pressure. With shelves and organ positives , two bellows are usually operated by the Kalkanten by hand or by the player himself with his feet. If centrifugal blowers are used in new organ-positive buildings, on the other hand, shelves can only sensibly be supplied with "hand-drawn" play wind. On the one hand, reed whistles react much more clearly to mechanical wind than lip whistles, on the other hand, in some cases a thin bellows plate ensures an additional, desired, light resonance behavior, which is perceived as additional "liveliness" when the bellows are changed.
- Wolfgang Adelung: Introduction to organ building. Breitkopf & Härtel, Wiesbaden 1991, ISBN 3-7651-0279-2 (2nd revised and expanded edition. Ibid 2003).
- Hans Klotz : The book of the organ. About the nature and structure of the organ work, organ maintenance and organ playing. 14th edition. Bärenreiter, Kassel u. a. 2012, ISBN 3-7618-0826-7 .
- Johann Gottlob Töpfer : Textbook of organ building art. 3. Edition. Rheingold, Mainz 1939.
- Musical acoustics. Fraunhofer Institute for Building Physics (IBP)
- Wind generation ( Memento from February 15, 2011 in the Internet Archive )
- Vox Maris - the voice of the sea ( memento from August 24, 2015 in the Internet Archive ) on the Hey Orgelbau website
- Walter Vonbank: Restoration Report, Triebendorf 2007, p. 25.
- Information on the website of Orgelbau Kuhn , accessed on August 2, 2014.
- Description of the wind throttle at the organ in Denstedt , accessed on January 28, 2017