Each pipe organ has been individually crafted for the customer. Picture
yourself going to a tailor where not only is your suit custom made, but the
fabric is custom woven as well. The quality-oriented builder works with the
customer's needs and wants to produce the best organ that the budget can allow.
The architecture and acoustics of the room are factored into the organ's design.
The different sounds are chosen together by the builder and the customer.
When you look at the instrument, you can notice immediately if it is a
free-standing organ or a built-in instrument. A free standing instrument has a
case that is built to house all the pipes and parts that make the organ work.
This picture of the new Dobson instrument at the University of South Carolina is
an excellent example of a free-standing organ. The case acts as a sounding board
to focus and project the sound, much like the wood of a violin or guitar.
A built-in instrument is literally attached to the building. In the picture of
the Holtkamp, you can see that there is no case around the organ. The screened
doors on the bottom half are hiding the motor and parts that supply wind to the
pipes. There are also some pipes behind these screen doors. The Shantz is
typical of a church organ. The motor and wind supply parts are in other parts of
the church. The blower, which supplies the wind, is in the basement. Pipes line
the chancel with more pipes in chambers on the left and the right, behind the
vertical wooden blinds on the side edges of this picture.
What are these wooden blinds? These are shutters or shades. Because they are
always found covering the part of the organ called the swell, they are often
called swell shades. However, they can be placed in front of the Choir and Solo
divisions. They are strictly functional. When the shades are closed, the sound
from the pipes can't get out so it will be fairly soft. As the organist opens
the shades, the sound gets louder.
Swell shades are not to be confused with pipe screens, which are purely
cosmetic. In the picture of the Dobson, you can only see the pipes in the front
row. All gaps are filled in by the red lattice. This lattice, together with this
first row of pipes, is the pipe screen. Although you can't see behind the
screen, the sound can still get out. The pipe screen is useful when the builder
wants to hide the other parts of the organ which are not as attractive as the
pipes.
Many different materials for pipe screens have been used. Most builders use wood
carvings or metal shaped into intricate patterns. I have even seen cloth but
that is not a good screen because it muffles the sound. The pipe screen is there
to make the organ attractive, not detract from the sound. The Dobson pipe
screens are unique because they are pieces of painted PVC pipe with wood joining
them together on the backs of the pieces.
Pipe screens often use the first row of pipes, artistically arranged, as part of
the screen. However, some builders will not use the front pipes to hide others
and will put a large screen in front of the whole organ. A instrument in First
Scots Presbyterian in Charleston, built by Ontko and Young, has a large,
beautiful, white wrought-iron decorative screen. In many organs, including the
Dobson example, these pipes are part of the organ and will speak. In some older
organs from previous centuries, small pipes were used to fill in the gaps. These
were fake pipes because they did not speak. In the 1800s, it was common to have
the front row make of speaking pipes but to paint decorative designs on the
pipes. The paint does not affect the sound. Today, most builders prefer to
polish the pipes.
During this century, a push to expose the organ took place. One builder,
Holtkamp of Cleveland, did not use pipe screens but arranged his pipes
asymmetrically. He also put the swell shades in full view of the audience. He
felt it would be more exciting if the audience could see the organist open the
shades and hear the music getting louder simultaneously. The picture of the
Shantz also does not have any pipe screens.
The Console
In the picture of UK's Holtkamp, you can see that the manuals and pedals are
some distance away from the actual organ. The entire unit, keys, buttons, knobs
and all, is called the console. It has everything the organist needs to control
the organ. This one can be moved around the stage. Organs can also have an
attached, non-movable console, which the Dobson has. The manuals usually have 61
notes, 30 less than a piano. The pedals duplicate the bottom 32 notes of the
manuals but have their own sounds, separate from the sounds of the manuals. The
different kinds of sounds available are called the stops. On the Holtkamp, they
are the tabs above the manuals. On the picture of the Shantz console, they are
the drawknobs on the left and right of the console.
Sound on the organ is produced when the wind passes through the pipe. The
process of getting the wind to that pipe follows this path: First, a motor blows
air into a reservoir. This picture is the air reservoir from the Holtkamp at the
Univ. of KY. Notice the weights that look like bricks on the top. These weights
keep the air under pressure so that the sound does not waver. From the
reservoir, the air moves into the wind chest, which is a box with rows of holes
on the top. The pipes stand on top of the wind chest, one pipe to a hole. To
make the pipe speak, the wind must move from the wind chest to the pipe. If the
holes connecting the pipes to the wind chest remained open all the time, all the
pipes would speak at once whenever the organ was turned on. There are two
mechanisms that control two separate barriers to the flow of air from the wind
chest to the pipe: stop action and key action.
Stop Action
The holes in the top of the wind chest have a movable barrier that is
controlled by the drawknobs or tabs on the console. When a stop is turned off,
the barrier blocks the holes. By pulling the stop out, or the "on"
position, the barrier between the air supply and the holes moves so that the
wind can get to the pipes. The organ has a separate stop action for each stop in
the organ. The organist could remove the barrier to several sounds by turning
their corresponding stops on. This would allow several pipes to speak at once
when only one note is played.
There are different kinds of wind chests and the stop action for each kind works differently. To give a better illustration of stop action, here is Lynn Dobson's explanation of a slider chest from an interview.
In a mechanical action organ, the wind chest where the pipes stand is called a slider chest. And a slider chest means that it uses a long strip of wood called the slider. It has a hole for every note on the keyboard, or in other words, a hole for every pipe in the rank. If you pull the draw knob out, you actually physically move the slider from one side to the other. A series of holes line up so that when you play a note on the keyboard, air can pass from the wind chest below to the pipe above. If you push the stop off, then the slider moves a few inches over to the side and the air can't pass from the air chamber up to the pipe. So in this manner, if you pull on one draw knob, then you turned on one rank of pipes so you have one pipe playing from each note. If you drew two stops, there would be two pipes from each note and of course if, on this organ, you drew 30 stops, you could actually have 30 pipes playing from one note on the keyboard.
Of course, the organist needs control over each note individually. The stop action removes the barrier to all the pipes of one stop. These pipes cannot be allowed to speak all at once or there would be no music. The key action works with the stop action. After a stop is turned on, and the barrier to the holes is removed, the key action can control the wind flow to the pipe. When the key is depressed, it opens a valve beneath the pipe so that the wind can finally get through the hole in the wind chest. However, a stop must be on, removing one barrier to the pipe. If no stops are on, there will be no sound, even though the valve is opening when the key is pressed. Different styles of building over the last 400 years have resulted in two kinds of key action: Mechanical and Electropneumatic.
While the wind supply, stop action, and key action have many parts, most of the space in the organ is occupied by the pipes.
