The Recent Revolution in Organ Building - George Laing Miller

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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.

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      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.

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      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 it would never do to put all the large pipes (because of their weight) at one end of the wind-chest, they were usually divided between the two ends and it became necessary to transfer the pull of the keys sideways, which was done by a series of rollers called the roller-board. This, of course, increased the friction and necessitated the use of a still stronger spring. That with the increased area of the pallet is why the lower notes of the organ were so hard to play. And to the resistance of the spring must also be added the resistance of the wind-pressure, which increased with every stop drawn. When the organ was a large one with many stops, and the keyboards were coupled together, it required considerable exertion to bring out the full power of the instrument; sometimes the organist had to stand on the pedals and throw the weight of his body on the keys to get a big chord. All kinds of schemes were tried to lighten the "touch," as the required pressure on the keys is called, the most successful of which was dividing the pallet into two parts which admitted a small quantity of wind to enter the groove and release the pressure before the pallet was fully opened; but even on the best of organs the performance of music played with ease upon modern instruments was absolutely impossible.

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      Just as we no longer see four men tugging at the steering wheel of an ocean steamer, the intervention of the steam steering gear rendering the use of so much physical force unnecessary, so it now occurred to an organ-builder in the city of Bath, England, named Charles Spachman Barker,[1] to enlist the force of the organ wind itself to overcome the resistance of the pallets in the wind-chest. This contrivance is known as the pneumatic lever, and consists of a toy bellows about nine inches long, inserted in the middle of the key action. The exertion of depressing the key is now reduced to the small amount of force required to open a valve, half an inch in width, which admits wind to the bellows. The bellows, being expanded by the wind, pulls down the pallet in the wind-chest; the bellows does all the hard work. The drawing on the next page, which shows the lever as improved by the eminent English organ-builder, Henry Willis, shows the cycle of operation.

      When either the finger or foot is pressed upon a key connected with k, the outer end of the back-fall gg is pulled down, which opens the pallet p. The compressed air in a then rushes through the groove bb into the bellows cc, which rises and lifts with it all the action attached to it by l. As the top of the bellows cc rises, it lifts up the throttle-valve d (regulated by the wire m) which prevents the ingress of any more compressed air by bb. But the action of the key on gg, which opened the pallet p, also allowed the double-acting waste-valve e to close, and the tape f hangs loose. The compressed air, therefore, as it is admitted through bb cannot escape, but on the other hand when the key releases the outer end of g, and lets it rise up again, the tape f becomes tightened and opens the waste-valve, the bellows cc then drops into its closed position.

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