It will be seen, therefore, that the tone, quality, or timbre of an organ-pipe, and therefore of a "stop" or set of organ-pipes, depends upon skilled attention to at least six distinct considerations, viz.:—

It is the thorough mastery of the art of manipulating pipes, with all these essential points kept in view, which enables the voicer to produce the exquisite contrasts of tone heard in good organs between the tranquil Dulciana and the delicate Salcional; between the Violin Diapason and the Gamba; between the Keraulophon and the Viola, as variously constructed; between the fluty-toned stops, of wood or of metal, to which various names have been given: and the full chorus or combined power of a large instrument will be majestic, imposing, and dignified, or, on the other hand, shrill, harsh, and unpleasing (quality of materials being assumed to be similar), in proportion to the skill, taste, and judgment with which it is finally voiced and regulated.

We have said enough, perhaps, to justify our advice that metal pipes be procured in a finished condition from competent makers.

Our little organ contains two metal stops, viz. a Dulciana (or a small Open Diapason) from Tenor C to f in alt, and a Principal of 4 feet throughout. Each of these, made of good metal, should cost £6 or £7. Cheap pipes mean inferior metal, and this we cannot recommend in any organ, great or small. The nearer the approach made to pure tin the better (other essential points being assumed) will be the quality of the tone.

In ordering the pipes, the weight or pressure of wind on which they are to speak must be carefully specified. This may be easily ascertained by using a wind-gauge, a little instrument which we sketch in its simplest form in Fig. 45. It consists of a glass tube, bent as shown in the figure (this can be done at any glass-blower's or optician's), and having its lower end inserted in a wooden pipe-foot. Planting the gauge on any hole of full size in any part of the sound-board, we pour a little water into the bent part or dip of the gauge. On blowing the bellows steadily, and depressing the key on the manual corresponding to the groove on which the gauge is placed, the water will be depressed in the inner column, and will rise in the outer. By adjusting the weights on the bellows we may make this difference in the levels of the two columns greater or less as we please. In our organ we shall have a "2-inch wind;" that is to say, we shall load the bellows so that the gauge may indicate a difference of 2 inches between the two columns.

Fig. 45.

We may note here that about 7 lbs. per square foot of surface of top-board will be required to give this pressure. Pieces of old cast iron about an inch thick may be procured at any foundry, and form the most suitable material for weights.

The voicer having worked to a 2-inch wind, it is probable that when the new metal pipes are planted in their places they will speak with charming evenness and truth. If some or any of them, however, betray some defects, it will be well not to meddle with them until we have satisfied ourselves that the fault does not belong to our own mechanism. If, for instance, one pipe should be softer or less prompt and clear than the others, let us be sure that the flow of wind to that pipe is not interrupted or throttled by a chip in the wind-hole or (if there is conveyancing) in the channel. This will be ascertained by planting the pipe for the moment on some other groove than its own. If the holes and channels are all clear, and the pallet is opened freely by the key, the fault must be in the pipe. This may have suffered some little injury in the packing case, e.g. the lower lip may have been nipped too close to the edge of the languid, thus reducing the width of the windway. This may be carefully rectified with the flat blade of a common table-knife, or similar object. Or the languid itself may have been bent or depressed by the weight of another pipe, packed within it to save room in the case. If this is so, the languid must be carefully pushed back to the level by a stout wire or rod inserted through the foot-hole. If the upper lip has been pressed inwards, we must counsel the utmost care in bringing it back to its position. The pipe should be sent back to the maker if the distortion is serious or considerable. If it is slight we may rectify it by passing a slip of iron bent into the shape of the letter L through the mouth, and thus pulling forward the whole of the lower par of the "leaf," preserving its regular slope as before. If the mouth, lips, and languid are all right, it is possible that by some accident the size of the foot-hole has been reduced. It may be cautiously enlarged with a penknife or with a broach; and if under other circumstances the foot-hole requires reduction, this maybe done by gently rapping or hammering the metal round the aperture with the flat side of a chisel. The builders have a heavy brass cone for effecting this reduction called a "knocking-up cup." Similar brass cones, we may here add, are used in tuning. They are expensive, however.