[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 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.