The Recent Revolution in Organ Building | Page 4

into groups placed in various positions, each playable from a separate keyboard, and this practice prevails to this day. An average church organ will contain three or four wind-chests, each with its quota of pipes and designated as follows:
1. The Great organ, consisting of the front pipes and other loud-speaking stops. Back of this and usually elevated above the level of the Great organ pipes is
2. The Swell organ, all the pipes of which are contained in a wooden box with Venetian shutters in front, the opening or closing of which modifies the tone; below the Swell box is placed
3. The Choir organ, containing soft speaking pipes suitable for accompanying the human voice; and back of all or on the sides is
4. The Pedal organ, containing the large pipes played by the pedals.
Larger instruments have still another wind-chest called the Solo organ, the pipes of which are very loud and are usually placed high above the Great organ.
In some large English organs, notably that in the Town Hall of Leeds, a further division was effected, the pipes of the Great organ being placed on two wind-chests, one behind the other. They were known as Front Great and Back Great.
The original reason for dividing a church organ in this manner seems to have been the impossibility of supplying a large number of stops with wind from a single wind-chest.
It will thus be seen that our average church organ is really made up of three or four smaller organs combined.
The wind-chest is an oblong box supplied with air under pressure from the bellows and containing the valves (called pallets) controlling the access of the wind to the pipes. Between the pallet and the foot of the pipe comes another valve called the slider, which controls the access of the wind to the whole row of pipes or stop. The pallet is operated from the keyboard by the key action. Every key on the keyboard has a corresponding pallet in the wind-chest, and every stop-knob operates a slider under the pipes, so that both a slider must be drawn and a pallet depressed before any sound can be got from the pipes. The drawings will make this plain.
Fig. 1 is a front view and Fig. 2 a side view of the wind-chest. A is the wind-chest into which compressed atmospheric air has been introduced, either through the side or bottom, from the end of the wind-trunk B. The pallets, C C C, are held against the openings, D D D, leading from the wind-chest to the mouth of the pipes, by springs underneath them.
[Illustration: Fig. 1. The Wind-chest. Front View]
The spring S (Fig. 2) keeps the pallet C against the opening into D. The wires called pull-downs (P, P, P), which pass through small holes in the bottom of the wind-chest and are in connection with the keyboard, are attached to a loop of wire called the pallet-eye, fastened to the movable end of the pallet. A piece of wire is placed on each side of every pallet to steady it and keep it in the perpendicular during its ascent and descent, and every pallet is covered at top with soft leather, to make it fit closely and work quietly. When P is pulled down (Fig. 1) the pallet C descends, and air from the wind-chest A rushes through D into the pipe over it. But the slider f is a narrow strip of wood, so placed between the woodwork g and h that it may be moved backwards and forwards from right to left, and is pierced with holes corresponding throughout to those just under the pipes. If the apertures in the slider are under the pipes, the opening of a pallet will make a pipe speak; if, however, the slider has been moved so that the apertures do not correspond, even if the pallet be opened and the chest full of air from the trunks, no sound will be produced.
[Illustration: Fig. 2. The Wind-chest. Side View]
When the apertures in the slider are under those below the pipe, the "stop," the handle of which controls the position of the slider, is said to be out, or drawn. When the apertures do not correspond, the stop is said to be in. Thus it is that when no stops are drawn no sound is produced, even although the wind-chest be full of air and the keys played upon.
This wind-chest with the slider stop control is about all that is left to us of the old form of key action. The pallets were connected to the keys by a series of levers, known as the tracker action.
There were usually six joints or sources of friction, between the key and the pallet. To overcome this resistance and close the pallet required a strong spring. Inasmuch as