Reference Material
For The Organ Committee And Architect
Parts of the organ
- Console
- Cabinet containing keyboards and stop controls.
- Pipes
- Pipes are best placed in a free-standing wooden case within the main body of the room. They are sometimes placed in a chamber, which is a separate room located outside the main listening room. Most pipes are made of metal. Wood is used for some large pipes because of its stiffness and for a few small pipes because of its mellow tonal qualities.
- Mechanism
- Blower, wind pressure regulators (reservoirs, bellows), chests, shutters, etc. Chests are airtight boxes on which the pipes stand. Chests contain valves which, on signal from the console, let wind to the pipes.
Types of organs
- Mechanical action
- Also called tracker action. Keys are attached by mechanical linkage directly to valves in chests. Distances must be kept short. Mechanical action was used for hundreds of years before the use of electricity, which occurred around 1900, and is still the favorite system for many organists because it allows more direct control of the valves.
- Electric action
- Called electro-pneumatic action if pneumatic assists are involved. Allows console to be separated from pipes, although at some loss of control and intimacy for the organist. Electric action should not be confused with electronic organs, which use electronic generators and loudspeakers instead of pipes for tone production.
Location
Pipes should be placed:
- above and behind the choir;
- on a line of sight to the listeners;
- so that they speak directly down the length of the building;
- in a wooden case;
- within the walls of the listening room, not in separate rooms (chambers);
- with large pipes visible in front, small pipes behind.
Sound comes from the mouth, not the top, of a flue pipe. Pipe mouths should be about 2' above the tallest choir singer, higher if the building is long.
Since an organist's ears face forward, the console should be placed so that the organist faces the pipes and, if possible, the choir and choir director. Facing the altar, ushers, congregation, etc. is not as important as facing the music.
Space requirements
It is very important that the architect consult with the organbuilder before plans for the building are drawn.
Organs can have from 1 to as many as 6 or 7 departments or divisions (groupings of pipes, each grouping represented by one keyboard). Most organs have 3 or 4 departments. Buildings seating more than 300 to 500 normally have 4 departments, which means a console with 3 manual keyboards plus pedal.
It is convenient to think of the organ as being made up of building blocks, one for each department.
Example: a medium size 2 manual and pedal organ = 3 departments = 3 building blocks.
The top manual keyboard, called Swell, plays pipes located in an enclosure with shutters across the front which can be operated by the organist to regulate or "swell" the loudness. The typical Swell department is 8' wide, 10' high, and at least 6' deep. Because of the enclosure, the Swell cannot be placed in front of another department. Space requirements of the lower manual keyboard, called Great, and Pedal are similar to those of the Swell. The Pedal, however, can sometimes be split into 2 parts.
Pipes and chests
Each stop name has a number which indicates the speaking length of the longest pipe of that stop. Example: the body of the longest pipe of a Principal 8', whose pipes are open at the top, is between 94" and 100" (see drawing). Additional space is required for the pipe's foot, clearance at top of pipe, and chest. Therefore a Principal 8' requires about 10' height.
The tops of some pipes are stopped for tonal reasons. The bodies of those pipes are about half the length of open pipes. Example: the body of the longest pipe of a Bourdon 8', whose pipes are stopped, is about 50" long.
Chests are 6' to 10' wide, 2' to 8' deep, depending on the number of pipes on the chest.
Keys can be in a console which is detached from the pipe enclosure (detachment is possible only with electric action) or on a keydesk which is attached to the pipe enclosure. A console requires floor space 5' to 6' square. A keydesk extends about 4' from the pipe enclosure.
The floor beneath the pedalboard and bench must be firm and non-resonant, and it must not be carpeted.
Every statement and dimension given above may vary, depending on the design of the organ: Departments may be called by other names. Shutters may be in front of departments other than the Swell, or there may be no shutters. Some small organs occupy a floor space no larger than 6' wide and 18" deep, plus 4' for keydesk, pedalboard, and bench.
HVAC (heating, ventilating, air conditioning)
Pipes should receive the same treatment as if they were people: about 72° F., no drafts. The best arrangement is to place supply registers higher than the highest part of the organ but not blowing directly onto pipes or into cases or chambers and to place return-air registers lower than the lowest part of the organ, preferably inside the pipe enclosures. Closed parts of the organ, particularly the Swell, may require supplemental circulation by addition of a quiet centrifugal blower.
Temperature stratification is not a problem for European organs because of the absence of HVAC systems. In America, however, temperature stratification is of major importance, especially in the middle of the continent where temperatures are extreme. It is therefore best to place all the chests at the same elevation so that all the pipes get the same temperature. If pipes are stacked, with some pipes higher than others, out-of-tuneness is inevitable. An instrument which is not in tune is a failure.
It is not necessary to heat or cool the organ except when it is to be played for public use. Neither cold nor hot air hurts the organ; it only causes the organ to sound out of tune. Playing the organ when it is hot or cold will not hurt it. When the temperature of the air around the pipes returns to the same level as when the organ was tuned, the organ will again sound in tune.
Normal humidity fluctuations are generally not a problem. However, problems from wood expansion and contraction due to humidity extremes often occur in buildings which are heated (dry) or cooled (damp) for long periods, say several weeks.
Acoustics
The acoustics of the room are as important to the success of the organ as the design of the organ itself. An absorbent surface is to sound what an open window is to air-conditioning or black paint is to lighting.
If people are to sing, the room must make them feel part of a group, not isolated. This is accomplished by using non-absorptive wall, floor, and ceiling surfaces without carpet, absorbent tile, or drapes. Walls and ceiling must be stiff as well as hard. This is especially important for sustaining the low frequency, long wavelength bass tones which give amateur singers security. The organ will sound its best in a room which is good for singing, one that has reverberation and which does not absorb sound.
All of the sound producers — preacher, choir, organ — should have rigid, stiff, hard surfaces behind them in order to project their sounds toward the listeners.
Electrical requirements
Console: two 120 volt AC convenience outlets, one inside the cabinet and one accessible to the organist. Switch for blower may be located outside the console, if convenient to the organist.
Pipe case or chamber: blower motor, typically ½ to 2 h.p. 220 volt AC 3 phase, switched from console; organ DC power supply, usually called rectifier, typically 5 to 10 amp 120 or 220 volt AC single phase, switched with blower; service lamps and outlets. Control circuits for the organ are 12 to 15 volt DC, supplied by organbuilder.
Access and service
Space must be allowed for access, usually from behind the case. It is tempting to put small pipes in front so that pipes can be reached for tuning by standing on a ladder in front. The sound is better, however, if the Principal ranks with the largest pipes are in front.
Case design
The case is designed by the organbuilder in consultation with the architect and client. The choice of wood is based on that used for the other furniture. The difference in acoustical properties of different woods is not significant. Visible front pipes can be of wood or metal — polished tin (actually a tin/lead alloy), polished zinc, polished aluminum, polished copper, or flamed copper. Gold colored pipes of 60 years ago, made by coating zinc with powdered bronze and varnish, are usually rejected in favor of natural metals.
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