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Pittsburgh Area Theatre Organ Society, Inc. |
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HOW PIPE ORGANS WORK |
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When we experience the magic of a theater pipe organ installed in a movie palace, we see the organ console down by the stage and we hear the music emanating from various locations around the auditorium. But what is an organ? What are its parts? And how does it all work? The smallest and simplest unit instruments of this type were self-contained cabinet instruments, placed in the orchestra pit, and usually equipped with just a few ranks of pipes and some traps, all played from an attached modified upright piano console. Many were also equipped with a player mechanism, and punched paper rolls could (and frequently did) serve as a substitute for a human performer. These instruments were designed for small houses where this kind of instrument represented a significant improvement over the upright piano which it replaced. Unfortunately, very few instruments of this type have survived, although many thrilled movie patrons in smaller theatres in the early years of the 20th century. Larger organs were installed in a far more complex manner. Various components of the organ were installed in remote areas of the theatre. Here follows a brief description of these components, and their function. Console The organ console is the large keydesk from which the organist controls and plays the organ. Most commonly, it has two or three manuals (keyboards), although quite a few large installations had four manuals. A few even had five manuals! The manuals are surrounded by a semicircle arrangement of stop tabs. There is also a large pedal board (a keyboard played with the feet) and many other buttons and pedals that control the swell shutters, sound effects, and mechanics of the instrument. Typically, the console is located on a large lift mechanism, similar to an elevator, which allows the console to be raised for solo performances and lowered during the movie or when not in use. The "brains" of the organ are in the relay. It takes electrical signals from the console, generated whenever keys are depressed or stops are changed, and directs the correct pipes and/or traps to instantly sound. Originally, the relays were electro-pneumatic contraptions but often have been replaced with computerized systems.. Blower This is the large fan which provides the pressurized air which will blow through the pipes. It also provides air to operate the mechanical devices which "play" the pneumatically-operated instruments (traps). Pressurized air is also used to perform other mechanical tasks, such as the operation of the swell shutters and the registration pistons that automatically change many stops at the press of a button. (The numbered navigation buttons on these web pages are replicas of the pistons found on a theatre organ console.) Windchest This is a wooden reservoir that contains pressurized air from the blower. Valves in the windchest are opened and closed remotely by the relay to cause the correct pipes to sound when the organist depresses the keys. A set of pipes that produces the same distinctive sound from the lowest to highest note is known as a rank of pipes. Most ranks contain 61 or 73 pipes. Small theatre pipe organs could have as few as three or four ranks of pipes, and the largest instruments had over fifty ranks. In actual numbers of pipes, a small instrument might have 100-300 pipes, while the largest instruments contained ten times that number. The highest sounding pipes are smaller than a pencil. The lowest bass pipes in large instruments are about 32 feet in length, and wide enough to allow a person to stand inside a pipe. Authentic percussion instruments such as piano, xylophone, orchestra bells, etc., are located in the pipe chambers. These instruments are played from the keys of the organ and made to sound by way of pneumatic action. Separate beaters or hammers are located above each metal or wooden bar on the pitched percussion instruments. Pneumatic action also controls the hammers that strike the strings of a real piano in the pipe chamber. Snare drum, bass drum, cymbals, and other percussion instruments are activated in the same manner. Sound effects such as siren, automobile horn, and train whistle, are all sounded from the organ console. These various components of the theatre pipe organ are often at a considerable distance from one another. They must be connected by miles of electrical wiring and lengthy wind lines. Publicity information about the 56-rank Wurlitzer in New York's Radio City Music Hall -- the largest original Wurlitzer installation -- states that there is more electrical wiring in that theatre organ than in all the rest of Rockefeller Center combined. |
