Grand Regulation – part XXX


Step no46 Check string level / damper seating  

Most technicians know that piano wire, even after being strung  and pulled up to tension, still retains a natural curve as a result of being reeled upon a spool during manufacturing. Because of this natural curve, the three strings (or two) which make a unison may or may not be perfectly level at the point where the hammers strike and where the dampers seat. Irregularities in string level may also be caused by the holes in the agraffes not being perfect.  Whatever the cause they must be corrected.  If one string in a unison is higher or lower than the others, problems in voicing and damper sealing are sure to result.
Since the string level affects both voicing and correct dampening, I find it easiest to match the string level to the dampers, then alter the tops of the hammers to finish matching the hammers to the strings. Theoretically, all strings should be perfectly level, with all of the tops of the hammers also perfectly level, and correct dampening on every note. However, being one who is more practical than theoretical, I have a tendency to leave the dampers alone if they are working fine! Play each note staccato, listening for the familiar “after ring” which tells that the dampers are not seating correctly. Don’t forget also to try the dampers using a lighter, legato touch, as well as using the sustain pedal. If any dampers are heard to “ring through,” feel the string directly in front of the damper head and check for a problem in the level of the strings. 
Not all problems with dampening are caused by string level. Sometimes the damper head is bent side to side or front to rear. Maybe the damper-to-string alignment is off. On trichords, if the middle string is dampened but one of the outer strings is not, try cutting the middle of the trichord a little deeper. There are numerous other reasons for incorrect dampening besides these. But if the strings are felt and one of the unisons seems to be too low or too high, try leveling the strings. When one string is low and the others are high, the obvious solution is to raise the low one. However, some technicians   would rather not raise two low ones to match one high string when one is high It is possible to lower one string. Whatever your preference, the end result should be to get all three unisons level.
To raise a low string, take a string hook, as used in restringing, and place it under the offending string between the agraffe and the damper. Slide it back and forth with a slight upwards motion a couple of times. This process is much like voicing in that you can always do a little more if needed, but it becomes a problem when you’ve gone too far. Don’t run the string hook too close to the agraffe as you want to put a slight bend in the wire rather than a crink. It is possible to break a weak agraffe, so put only a slight upwards pressure on the string. Retune the string and check for correct dampening.
As mentioned above, if one unison is high to the other two, you have a choice. The high string can be lowered, or the two lower ones can be raised with the method just shown. If you prefer to lower a high string, take something softer than the wire, a piece of brass or hard wood (not a screwdriver) and gently run it up and down the string using a slight downwards motion. This is a little trickier, and perhaps not as permanent as raising low wires. 
Step no47 Check sostenuto tabs for evenness, adjust knife angle  
The evenness of the sostenuto tabs should already have been checked while performing steps no43 & 44, the dampening lift form the key and lifter rail. If these previous steps were done correctly, all tabs will be in a straight line. If they are not, go back to step no43 and redo, as any change in the height of the damper lever to get good tab alignment will cause problems with the damper lift from the key and lifter rail.  
Adjusting the sostenuto knife angle rather simple. Adjustment is made by varying the length of the sostenuto pedal rod. Looking from the treble side of the piano at the rod, it should be at 5 o’clock in its rest position, 3 o’clock in the raised position. 
Step no48 Adjust sostenuto knife in / out and up / down  
Now that the tabs are perfectly even and the knife angle is adjusted, all that is left is the in/out and up/down adjustment of the sostenuto rod itself. Taken in this order, working on sostenuto systems becomes considerable less painful. If you can’t remember anything else about the sostenuto rod, remember the distance 1/8“. The rod cannot interfere with the normal playing of the piano. All tabs must clear the rod when not using the sostenuto pedal.  On the other hand, when the pedal is played, it must catch and hold firmly any tabs in the raised position. Adjust the rod in/out to give 1/8” clearance between the rod itself (not the knife part of the rod) and the ends of the tabs.
With the sostenuto pedal in the down position…
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