Damper lifter buttons sometimes hold the damper off the string. See
that the top button falls so low that the damper lever does not touch
it when the key is released. This is accomplished by altering the
lower button. Examine the damper felts to see if they are moth-eaten,
or have become hardened or in any way impaired. Notice the adjustment
of the shade; that it is not too low or too high. The purpose of the
shade is to prevent the damper levers from flying up; but it should be
high enough so that the levers do not touch it when the key is
depressed gently.

Defective damping is one of the most annoying conditions, and when one
is employed to regulate a piano thoroughly and put it in order, he
should see that no key is left in which this occurs. Strike each key
and immediately let it up to see if it stops the sound quickly, or, in
other words, damps perfectly; if it does not, find the cause and
regulate until satisfactory.

8. _The grand action_ being, in principle, practically the same as
that of the square and the upright, containing the same mechanism as
is found in those actions, it is needless to give special instructions
concerning it; as the previous work has given the pupil a thorough
knowledge of the requirements of all actions, their common faults, and
proper methods of regulating to bring about satisfactory results. Let
us merely remark: Study thoroughly the behavior of every component
part of each action that comes under your observation; understand what
each part is for, why it is there, and how it works or should work
properly to fill its office. Then regulate and try for results. If you
have natural mechanical genius, a little experience will prepare you
to do all regulating and repairing with skill and quickness.