Electro-pneumatic action
Encyclopedia
The electro-pneumatic action is a control system for pipe organ
s, whereby air pressure
, controlled by an electric current
and operated by the keys of an organ console
, opens and closes valves within wind chests, allowing the pipes
to speak. This system also allows the console to be physically detached from the organ itself. The only connection was via an electrical cable from the console to the relay, with some early organ consoles utilizing a separate wind supply to operate combination pistons.
and inventor, Robert Hope-Jones
. He overcame the difficulties inherent in earlier designs by including a rotating centrifugal air blower and replacing banks of batteries with a DC generator, which provided electrical power to the organ. This allowed the construction of new pipe organs without any physical linkages whatsoever. Previous organs used tracker action
, which requires a mechanical linkage between the console and the organ windchests, or tubular-pneumatic action
, which linked the console and windchests with a large bundle of lead tubing.
This pneumatically assisted valve action is in contrast to a direct electric action
in which each pipe's valve is opened directly by an electric solenoid
which is attached to the valve.
While many consider tracker action organs to be more sensitive to the player's control, others find some tracker organs heavy to play and tubular-pneumatic organs to be sluggish, and so prefer electro-pneumatic or direct electric actions.
An electro-pneumatic action requires less current to operate than a direct electric action. This causes less demand on switch contacts. An organ using electro-pneumatic action was more reliable in operation than early direct electric organs until improvements were made in direct electric components.
A disadvantage of an electro-pneumatic organ is its use of large quantities of thin perishable leather, usually lambskin. This requires an extensive "re-leathering" of the windchests every twenty-five to forty years depending upon the quality of the material used, the atmospheric conditions and the use of the organ.
Like tracker and tubular action, electro-pneumatic action is less flexible in operation than direct electric action, in which each rank operates independently, allowing "unification", where each individual rank on a windchest can be played at various octave ranges.
A drawback to older electric action organs was the large amount of wiring required for operation. With each stop tab and key being wired, the transmission cable could easily contain several hundred wires. The great number of wires required between the keyboards, the banks of relays and the organ itself, with each solenoid requiring its own signal wire, made the situation worse, especially if a wire was broken (this was particularly true with consoles located on lifts and/or turntables), which made tracing the break very difficult.
These problems increased with the size of the instrument, and it would not be unusual for a particular organ to contain over a hundred miles of wiring. The largest pipe organ in the world, the Boardwalk Hall Auditorium Organ, is said to contain more than 137500 miles (221,284.3 km) of wire. Modern electronic switching has largely overcome these physical problems.
, and later, integrated circuit
s and microprocessor
s, miles of wiring and electro-pneumatic relays have given way to electronic and computerized control and relay systems, which have made the control of pipe organs much more efficient. But for its time, the electro-pneumatic action was considered a great success, and even today modernized versions of this action are used in many new pipe organs.
The Contemporary American Organ by William H. Barnes
Pipe organ
The pipe organ is a musical instrument that produces sound by driving pressurized air through pipes selected via a keyboard. Because each organ pipe produces a single pitch, the pipes are provided in sets called ranks, each of which has a common timbre and volume throughout the keyboard compass...
s, whereby air pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
, controlled by an electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
and operated by the keys of an organ console
Organ console
thumb|right|250px|The console of the [[Wanamaker Organ]] in the Macy's department store in [[Philadelphia]], featuring six manuals and colour-coded stop tabs....
, opens and closes valves within wind chests, allowing the pipes
Organ pipe
An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air is driven through it. Each pipe is tuned to a specific note of the musical scale...
to speak. This system also allows the console to be physically detached from the organ itself. The only connection was via an electrical cable from the console to the relay, with some early organ consoles utilizing a separate wind supply to operate combination pistons.
Invention
Although early experiments with Barker lever, tubular-pneumatic and electro-pneumatic actions date as far back as the 1850s, credit for a feasible design is generally given to the English organistOrganist
An organist is a musician who plays any type of organ. An organist may play solo organ works, play with an ensemble or orchestra, or accompany one or more singers or instrumental soloists...
and inventor, Robert Hope-Jones
Robert Hope-Jones
Robert Hope-Jones , is considered to be the inventor of the theatre organ in the early 20th century...
. He overcame the difficulties inherent in earlier designs by including a rotating centrifugal air blower and replacing banks of batteries with a DC generator, which provided electrical power to the organ. This allowed the construction of new pipe organs without any physical linkages whatsoever. Previous organs used tracker action
Tracker action
Tracker action is a term used in reference to pipe organs and steam calliopes to indicate a mechanical linkage between keys or pedals pressed by the organist and the valve that allows air to flow into pipe of the corresponding note...
, which requires a mechanical linkage between the console and the organ windchests, or tubular-pneumatic action
Tubular-pneumatic action
"Tubular-pneumatic action" refers to an apparatus used in manypipe organs built during the late 19th and early 20th centuries. The term "tubular" refers to the extensive use of lead tubing to connect the organ's console to the valves that control the delivery of "wind" to the organ's pipes...
, which linked the console and windchests with a large bundle of lead tubing.
Operation
When an organ key is depressed, an electric circuit is completed by means of a switch connected to that key. This causes a low-voltage current to flow through a cable to the windchest, upon which a rank, or multiple ranks of pipes are set. Within the chest, a small electro-magnet associated with the key that is pressed becomes energized. This causes a very small valve to open. This, in turn, allows wind pressure to activate a bellows or "pneumatic" which operates a larger valve. This valve causes a change of air pressure within a channel that leads to all pipes of that note. A separate "stop action" system is used to control the admittance of air or "wind" into the pipes of the rank or ranks selected by the organist's selection of stops, while other ranks are "stopped" from playing. The stop action can also be an electro-pneumatic action, or may be another type of actionThis pneumatically assisted valve action is in contrast to a direct electric action
Direct electric action
Direct electric action is one of various systems used in pipe organs to control the flow of air into the organ's pipes when the corresponding keys or pedals are depressed...
in which each pipe's valve is opened directly by an electric solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
which is attached to the valve.
Advantages and Disadvantages
The console of an organ which uses either type of electric action is connected to the other mechanisms by an electrical cable. This makes it possible for the console to be placed in any desirable location. It also permits the console to be movable, or to be installed on a "lift", as was the practice with theater organs.While many consider tracker action organs to be more sensitive to the player's control, others find some tracker organs heavy to play and tubular-pneumatic organs to be sluggish, and so prefer electro-pneumatic or direct electric actions.
An electro-pneumatic action requires less current to operate than a direct electric action. This causes less demand on switch contacts. An organ using electro-pneumatic action was more reliable in operation than early direct electric organs until improvements were made in direct electric components.
A disadvantage of an electro-pneumatic organ is its use of large quantities of thin perishable leather, usually lambskin. This requires an extensive "re-leathering" of the windchests every twenty-five to forty years depending upon the quality of the material used, the atmospheric conditions and the use of the organ.
Like tracker and tubular action, electro-pneumatic action is less flexible in operation than direct electric action, in which each rank operates independently, allowing "unification", where each individual rank on a windchest can be played at various octave ranges.
A drawback to older electric action organs was the large amount of wiring required for operation. With each stop tab and key being wired, the transmission cable could easily contain several hundred wires. The great number of wires required between the keyboards, the banks of relays and the organ itself, with each solenoid requiring its own signal wire, made the situation worse, especially if a wire was broken (this was particularly true with consoles located on lifts and/or turntables), which made tracing the break very difficult.
These problems increased with the size of the instrument, and it would not be unusual for a particular organ to contain over a hundred miles of wiring. The largest pipe organ in the world, the Boardwalk Hall Auditorium Organ, is said to contain more than 137500 miles (221,284.3 km) of wire. Modern electronic switching has largely overcome these physical problems.
Modern methods
In the years after the advent of the transistorTransistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
, and later, integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s and microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
s, miles of wiring and electro-pneumatic relays have given way to electronic and computerized control and relay systems, which have made the control of pipe organs much more efficient. But for its time, the electro-pneumatic action was considered a great success, and even today modernized versions of this action are used in many new pipe organs.
Sources
- A Brief History of Electronics in Pipe Organs
- William H. BarnesWilliam H. BarnesWilliam Henry Barnes was a Union Army soldier during the American Civil War and a recipient of America's highest military decoration—the Medal of Honor.-Biography:...
- "The Contemporary American Organ" (1959) - George Ashdown AudsleyGeorge Ashdown AudsleyGeorge Ashdown Audsley was an accomplished architect, artist, illustrator, writer, decorator and pipe organ designer who excelled in many artistic fields but is perhaps best known today for having designed the Wanamaker Organ in Philadelphia.Born September 6, 1838 in Elgin, Scotland, apprenticed...
- "The Art of Organ Building" - George Laing Miller - The Recent Revolution in Organ Building (1909).
- Reginald Foort, - "The Cinema Organ," Second Edition, New York: The Vestral Press, 1970, pp 74–78.
External links
The Recent Revolution in Organ Building by George Laing MillerThe Contemporary American Organ by William H. Barnes