The escapement lever is then considered. The spring that governs it requires adjustment. It must be sufficiently strong to cause the hammer to dance and jump a little on the lever when the key is released. The escapement lever must also be regulated by means of the hook that is found at its rear end. There must be space enough between the hook and the lever to ensure that the catch of the hammer by the check is at all times free. The screw that regulates the rise of the escapement lever must also be attended to. It is necessary that the movement of the lever be arrested before the hammer has quite risen to the point of the trip up of the jack.
The after-touch under the front of the keys is regulated by means of paper punchings. If enough punchings are placed under the keys to make very hard pressure necessary to force a release of the hammer, then punchings of 1⁄32 of an inch in thickness must be removed to make the after touch correct.
The keys must also be made to descend evenly as judged from the top. Unevenness is corrected also by the judicious use of punchings. In regulating the dampers there are many small details to be watched. The lifter-wires must work freely in the bushings and the heads must lie straight upon the strings. This is especially important as regards the bass wedge-dampers. There must be a small space between the damper levers and the felted backs of the keys and the rise of the damper heads when the levers are lifted must be even and facile. The height of ascent of the damper heads must not exceed one-fifth of an inch, and a little more when the whole of them are lifted by the pedal-rod. The sostenuto rod must also be adjusted so that the damper lever tongues are caught when the rod is revolved. Care must be taken that the rod does not catch the tongues when the pedal is not in use.
The pedal mechanism is simple. It is essential to see that the feet work in the lyre without scraping; hence lubrication with graphite and tallow is necessary. The rods that connect with the action levers must so engage as to be just in contact without bearing too much. The soft “piano” pedal must engage with the shifting lever so as to allow a small space between it and the point of contact with the key-frame. The strength of the reaction spring in the case must be arranged so that the key-board is pushed back with promptness upon the release of the pedal. The “forte” pedal must be adjusted so that its connecting rod is in contact with the damper lever lifting rail, but not enough to operate without the depression of the pedal. The sostenuto pedal requires to be arranged to revolve the sostenuto rod instantly. Here the rod has to be revolved its entire distance before it operates and the adjustment may therefore be made quite close.
These directions will enable one at least to be sure that the regulation of a grand pianoforte action has been properly done; although it is not to be expected that the innumerable small details of practical work are to be learned other than practically. It must especially be borne in mind that the use of tools and facility in handling them and making definite adjustments with them is a matter of long and patient practice. The above instructions are intended merely to set the routine method before the reader, so that he may approach the subject with a correct knowledge of principles.
The regulation and adjustment of the upright action is precisely similar as to principles. The differences occur through the somewhat dissimilar method whereby repetition is attained and the great variation in the general position of the parts with reference to the strings.
The action of the upright is fastened, by means of the metallic brackets, to iron bolts which are set up in the key-bed. The height of these bolts depends upon the dimensions of the instrument and the striking point of the strings. In setting the action in place great care must be exercised in seeing that the hammer line lies truly in regard to the run of the strings. Errors in the casting of the plate often lead to a distortion of the true string-line and the action finisher must take care to set the action with due regard to these matters. When the action, which is minus hammers and dampers, is thus set in, the keys may be placed under it for the purpose of marking the points where the capstan screws or rockers must be set. The hammers and dampers are then glued in and adjusted for position with regard to the strings. If the action and keys are truly proportioned, it is always possible to make the length of the key just as recommended in the last chapter. Sometimes the size of the pianoforte makes impossible the employment of capstans or rockers with abstracts. In this case it is customary either to use a dowel prop or to lay the wippen directly upon the key. When the dowel prop is used it is driven firmly into the key, and its upper end, which is a wooden rod into which the lower spike is screwed, impinges against the wippen. In laying the place for the dowel to be driven, it must be remembered that it is necessary for the head of the dowel to hit the bottom of the wippen squarely. But the dowel describes a curve at its head when the key is moving, and the wippen has to be provided with a felted foot, curved so as to accommodate this circular motion of the dowel. This motion must be observed carefully, so that the dowel does not lay too far forward or back of the wippen foot when the key is at either of its extreme positions. The regulation proper now begins.
Abstracts, or dowels, are always regulated by a screw. This is either in the form of a capstan or of a rocker, or of the movable part of the dowel itself. The adjustment must be made with reference to the position of the jack under the hammer butt. It is necessary that the jack be just in contact with the notched heel of the butt. After the hammers and dampers have been put in and their positions with reference to the keys adjusted, it becomes necessary to regulate the escape of the hammer by means of the regulating buttons and the jacks. The directions given for grands apply here. The hammer springs must be put in place and the fall of the hammers noted. If they stick, the bushings are too tight or some cognate trouble exists which can be easily remedied with a drop of oil on the affected part.
The checks must be adjusted to the back-stops and made to stand square to them and they must also be arranged to catch the back-stops when the hammer has recovered about two-thirds of an inch from the string. We know that the length of the hammer blow should be from 1 24⁄25 of an inch in the bass to 1 9⁄10 of an inch in the treble.