Now the whole key-board being complete, no keys or points missing, it must be put on the musical box-plate, and the line of small dots, which every cylinder carries, will serve to indicate if all the points of the key-board occupy their right places. This can also be seen by the pegs; when the cylinder turns, the pegs must all come exactly under the middle of each point of the key-board.
When it is ascertained that all the points are in their places, the key-board must be finished completely, - that is, all missing spirals replaced, and the keyboard then definitely tuned.
The tuning must always be done twice, because all operations upon a key change its tone a little, even when a spiral is changed; and before hammering a key, it must be brought to the proper thickness and about to its right tone. It may be advisable here to remark that in the first tuning it is well to leave the key half a tone too high, because putting a spiral at its end lowers the tone, and in general it is easier to lower the tone than to elevate it.
The manner of repairing all defects in a musical box has now been indicated. The mechanical part now runs well, the key-board is repaired, tuned, and in good condition. Before indicating the form which must be given to the spirals of the key-board, and how to place the key-board itself in its right position, we offer the following suggestions.
The cylinder must be free to move easily up the 6, 8, or 10 tunes, as the case may be, and fall back readily to the first tune, being regulated by the spring at the left end of the cylinder. But care must principally be taken that the axis of the cylinder turns freely; on the other hand, it must have no play whatever to move lengthwise between the two bridges. If the least play exists, it will be utterly impossible to finish the box properly. The pegs of the cylinder must necessarily follow exactly under the points of the keys; if not, the box will never play well. If any play be found, it will easily be removed by bending the legs of one of the bridges of the axis.
This done, the spirals of the key-board must be bent their right shape, and the key-board put in its proper place. It will be well in a few words to describe the theory of the spiral, this being a very important part of the musical box. The manner in which these small steel stiflers are bent contributes very much toward making an excellent box. The upper side of the key-board must always make the same angle of the radius of the cylinder, passing through the point of the keys. This angle a, b, c, Fig. 209, must be 165°, or, which is the same thing, angle a b d equal to 15°. It is not very easy to measure this angle, but in practice the following will amount to about the same results. Supposing the diameter of the cylinder to be 2 1/8 in., a d must be £ in. It will be observed that the upper level of the key-board, 6 c, prolonged, will attain pretty exactly the summing of the spring at the end of the cylinder. Supposing this to be the case, the spiral must have the shape indicated in Fig. 210 magnified. The end of the spiral must be as near the point of the key as possible without touching it. It must be observed that the heavier a key is (or the lower the tone) the thicker must be the spiral, as it is more difficult to stop the vibrations of the key.
As the cylinder turns, the peg will first touch the spiral at about the last third part (in Fig. 210 the peg is at the place where it should commence to touch the spiral), the spiral will fall back, and when the peg has reached the end of the key, the vibration of the key will have stopped. If the spiral is too thin, the peg will readily pinch it (it must then be changed), and will not sufficiently stop the vibrations; or if too thick, the spiral itself will produce a buzzing noise in stopping the vibrations of the key. To see if the spiral has a good shape and works properly, it will be best to let the box play slowly, the key-board in its place, and examine how the pegs act on the spirals, and see that they do not get out of place. Some practice will be necessary here to find out if the spirals must be bent forward (when they do not sufficiently stop the vibrations), or backward (when they make too much noise, or are pinched). For bending these spirals a pair of pliers (Fig. 211) with a hook at each end will be necessary. It must not be forgotten that the shape and strength of the spiral, its distance from the end of the key, its place backward or forward, all have an importance which must not be overlooked.
The only thing remaining now is to put the key-board in its proper place. 1st. As to height. The dotted line which is found on each cylinder will here serve as a guide; but it must be observed that, supposing the shortest key to be on a level with the dots, the longest ones must be a little below, about the distance of half a dot. This difference in level gives the difference in "rise" of the keys, the longer ones necessitating more rise than the shorter ones. If this level should not be right, the key-board must be left as it is, and one of the bridges must be raised or lowered accordingly.
2nd. The key-board must occupy the right place, as to left and right. That is, all the pegs must pass directly in the centre of the points of the keys. It will facilitate matters to observe if the points of the keys pass at the same distance between the pegs of the two adjacent tunes. Should they not, the cylinder or the key-board must be shifted right or left; the key-board by bending the feet in the opposite direction, the barrel by filing or elevating the metal piece which rests on the tune counter placed on the inside of the toothed wheel of the cylinder.
3rd. A good rise must be given to the keys of the key-board. If they rise too little, they will have but little sound; if too much, they will have a disagreeable sound, and, moreover, it will be difficult for the spirals to stop the vibrations, or they will make a noise and get pinched. At the same time it must be carefully examined if the different keys produce their sound at the same moment; that is, in those parts of the tune when it is easy to observe that they should. This will be readily seen by letting the box play slowly. When the sounds are produced too late, the part of the keyboard where this occurs must be put a little backwards, and if too soon it must be put a little forwards. This is obtained by bending the feet of the keyboard in the opposite direction.
When the key-board is mended and tuned, it would 1e well to suggest that the spirals be bent only approximately, until after these last operations are completed, when the last touch must be given to the spirals, in order to obtain a musical box playing smoothly an 1 agreeably.
After all this is done, it would be well to let the box play through all the tunes, and correct all the pegs that may have lost their right position, either right or left, by producing a disagreeable noise, by touching the ends of the keys when they should not, or by playing too soon or too late. When they play too soon the pegs must be bent backwards; when too late, forwards.
The case may happen that 3 or 4 tunes play quite well, and at the fifth one, for instance, all the pegs pass over the side of the ends of the keys. This will be corrected by touching that part of the counting wheel which gives the said tune.
Let us now resume, in a few words, the order in which all these different repairs are to be effected.
First, repair all concerning the mechanical part of the box, until, without the key-board, every wheel runs well. See that the axis of the cylinder has no play lengthwise, then that the cylinder moves freely on its axis. Repair all missing keys and points of the keyboard, file the new keys half a tone too high, put all the points on a level and at the right distance from each other, place all the spirals, bend them appropriately, tune the keys definitely, put the key-board in its right place, finish the bending of the spirals to their proper shape, and then correct all pegs on the cylinder.
It often occurs when a musical box plays that the pleasure is destroyed by a continual buzzing noise, produced always by a piece of metal or wood not properly fastened. The best way to find out what part of the musical box produces this disturbing noise is to let the box stop, and make the keys resound from one end of the key-board to the other with a rounded point; the notes which cause this noise will soon be discovered, then continue with one hand to produce this sound, and at the same time with the other hand touch all possible parts of the box which seem to produce the noise, and as soon as, by touching, the noise ceases, the object has been discovered. Tightening the screw, or a drop of oil, will very often do away with the noise.