2. Their location in the organ must depend very much on special circumstances. When they can be placed in a row at the back of the instrument, their connection with the pedals becomes very simple, two sets of squares with trackers running under the bellows being all that will be necessary. If the room has abundance of height, the back set of squares may act on a roller-board, and then the pipes can be disposed symmetrically, the largest at each end.
3. The board on which they stand will not require a slider. It will be, in fact, a wind-chest only, a long box of stout pine or deal, having holes in its top countersunk to receive the pipe-feet. Under each hole is placed a pallet or valve, held up by a strong spring, and having a pull-down wire passed through a brass plate in the usual way.
The aperture of the wind-trunk is in the lower board of this chest, and over it, before the board is in place, is fitted a valve, faced with leather, and made to slide to and fro between guides. An iron spindle, turned to fit accurately in a brass collar, carries an arm jointed to the valve by a connecting rod or trace; and outside the chest it carries another arm, at right angles to this, jointed to the draw-stop handle or its trace. We have, in fact, a trundle passing air-tight through a collar, and by this simple contrivance we can shut off the wind at pleasure from the chest. Other methods of effecting this are in use, and may easily be devised. The pipes are very frequently placed on both sides of the organ, to the right and left. In this case the two chests will be at right angles to the manual chest or chests, and the action will be less direct. But it will be readily arranged as follows:—The pedal roller board will be long enough to act upon sets of squares, carried on the organ-frame to the right and left of the player, and at any convenient height. The other arms of these squares act by trackers on roller-frames placed under the chests.
There are cases in which this roller-board will be better placed at the back of the organ, the connection between it and the pedals being by squares and trackers; and there are also cases in which a large roller-frame lying upon the ground under the bellows may be made to answer every purpose. Bell-cranks, or horizontal squares, may also transmit the pressure of the foot on the pedal by other squares and trackers to the pedal pallets in a manner analogous to that of the draw-stop action, Fig. 49. There is abundant room for ingenuity and contrivance in all these details; the essential points are strength, quietness, and accessibility for repair or adjustment.
Some of our readers may be able to indulge in the luxury of a second pedal stop. This should be a Violoncello in metal, of 8-feet tone and length. In this case the pedal chest or chests will be regular sound-boards, with sliders; or the Sub-bass may be on a chest as already described, while the Violoncello may be on another, with two actions.
We have only to add, that the power and effectiveness of small organs may be increased by the contrivance called a "Terzo Mano" (Third Hand), or octave coupler. Let us suppose that an ordinary action has been fitted with backfalls in the usual positions. Then a second bridge, rising and falling by a draw-stop, is introduced, carrying skew backfalls which act on the pull-downs an octave higher than the first set. Thus the key CC will take down the Tenor C note, and so on throughout the scale. It is evident that the effect on the ear will be nearly, though not quite, the same as if each 8-feet stop had its corresponding 4-feet stop drawn with it. An Open Diapason will sound like an Open Diapason and Principal; a Stopped Diapason, like a Stopped Diapason and Stopped Flute, &c. To render the illusion complete, the pipes should be carried up twelve notes higher than the apparent compass of the key-board, that is to say, if the key-board has fifty-four notes the sound-board should have sixty-six grooves.
In a similar way the pedal Sub-bass may be made to play in octaves, producing the effect of a Sub-bass, 16-feet tone, with a Flute-bass of 8-feet tone added to it.
Of all such mechanical devices it must be said, finally, that neatness, accuracy, and noiseless precision of action are the conditions necessary to complete success.