Piano Action Regulation Checklist

Most people are aware of the need to tune pianos
regularly. What they often do not realize, unfortunately, is
that tuning is only a small part of the care needed to keep
a piano in first-rate condition. Poorly regulated pianos are
a nightmare for the performer, often making it impossible
for him to give his listeners a meaningful musical
experience. Equally important, they hinder students in their
efforts to develop technique, for many ways of playing are
impossible when the regulation is faulty.

A common misconception is that when a knowledgeable
pianist asks the technician to make some changes in the
regulation of a piano, it is because he wants the piano to
be specifically adjusted to his own personal preferences.
While personal preferences of course do exist, the
average piano is so far from being regulated in
accordance with the normal, correct standards that the
pianists request are usually just a desperate attempt to
restore these standard, reasonable norms.

Strike each note on the piano very forcefully, release it
very slowly, and then play it a second time FF. Notes
which fail to play on the first blow probably have the jack
too far forward, those which fail on the second probably
have it set too high. Since this will be the only test in which
all the notes of the piano will be struck, check at the same
time for missing ivories or strings, clicks or vibrations,
notes that do not function, etc.

Press down the damper pedal (on right) and place a stack
of twelve pennies at the front edge of a white key.
Gradually add pennies, one by one, until the key starts to
move down. It should take at least 13 and no more than 19
pennies to start the key moving. Check a number of
different keys. Adjacent keys should not vary more than the
weight of two pennies. After the key has moved down,
remove one penny at a time until the key rises almost
completely to its rest position. There should be an absolute
minimum of 6, preferably 7 pennies left on it. Be careful not
to allow pennies to fall between keys!

note - Ideally, the touch-weight of a grand piano should
be smoothly graduated from slightly heavier in the low
bass to slightly lighter in the high treble. In the center of
the keyboard, a touchweight of about 50 grams is
generally considered about right with the ends of the
keyboard differing by no more than about 5 grams. Since
the average penny weighs about 2.64 grams, 19 pennies
is about right near the center of the keyboard, but a
penny or two either way would not necessarily be
considered abnormal. 13 pennies (about 34 grams)
would be much too light. When removing pennies for the
second part of this test, bear in mind that up weight
should be roughly half of downweight, so if it takes 20
pennies to start the key moving downwards it should be
able to lift approximately 10 pennies. Finally, since
toughweight is to a large extent dependant on the weight
of the felt hammers, excessively low touchweight may be
an indication of badly worn hammers.

To measure the striking distance simply take a piece of
stiff paper or a doctor's tongue fall depressor, measure off
1 3/4" with a pencil, and insert it between two strings until it
barely rests on the surface of the hammer. The pencil mark
should then be even with the underside of the string. It is
even easier to measure if you if you make a notch at the
correct distance. You can feel the string with the notch and
observe the bottom end, which should just touch the
hammer. The distance should be within 1/8" of the 1 3/4"
standard. Check with the eye to see that the hammer line is
perfectly level and even. If the hammer shanks (the long
arms to which the hammer heads are attached) are resting
on the felt cushions below them, it is almost certain that the
hammers are resting too far from the strings, as there
should be a gap of roughly 1/4" between the shanks and
the cushions. This and some other measurements are
difficult to measure in the low bass and high treble, so it
may be best to confine your checking to the middle
registers.

Press down a key very slowly, observing carefully where
the hammer stops rising and starts to fall back down. This
should be 1/16" from the string, the thickness of a penny.
Up to 1/8" is acceptable for any note and for the low bass
notes with single strings, even slightly more than 1/8".
Check many notes to see that this adjustment is even.
Listen carefully while pushing the key down, especially
near the bottom of the key, where resistance increases.
Any creaking or squeaking indicates the need for
lubrication.

Again depress a key very slowly, and this time observe
how far the hammer falls after it changes direction. This
should be at least 1/16" and not more than 3/16" at the
most. Depress and hold down a chromatic series of
notes in this manner, and check to see that the hammers
all end up in a straight line. If you play any of the notes too
strongly when doing this, they will be caught by the
backchecks and appear to be much too low, so if any of
them seem far out of line, try them again even more
gently. After the hammer drops, it should be possible to
push the key slightly further down before hitting bottom.

Regular adjustment of a piano is necessary because the
mechanism contains many felt and leather parts that
become compressed and worn through use and are
considerably affected by varying moisture content due to
seasonal changes in the relative humidity of the air.

Strike a fairly hard blow, keeping the key down. The
hammer should be caught firmly when it rebounds and not
bounce back up toward the string. It should be caught
clearly higher than the half way point between the resting
point of the hammers and the strings, ideally about 5/8"
from the strings. Now play a series of notes simultaneously
and check to see that the line of caught hammers is
reasonably straight. (A deviation of 1/8" or so would be
acceptable in this case while it would not be in tests 3, 4,
or 5).

Strike a firm blow and then very gradually start to release
the key, observing the hammer carefully. At a certain
moment it should start to rise on its own. This motion
should be gradual, not jerky, but also not too slow, perhaps
about like a rather slow gesture by a conductor. Check for
evenness, as usual. It is impossible to judge the springs if
the back-checks are not working properly.

Place a stack of six pennies on a white key, and press it
down until it touches bottom securely, but without pushing
too hard. The surface of the top penny should be even with
the adjacent keys, or slightly lower, particularly on concert
grands. It should not be lower than the bottom surface of
the ivory key covering. A depth of seven pennies (about
.420") would be the absolute maximum permissible for a
concert grand, and would definitely be too deep for
smaller instruments. Check with the eye to make sure the
keys are level both when at rest and when depressed.
Check the touch depth in the middle and at the extreme
ends of the keyboard, as it may be off in one place more
than another. Finally, press some black keys down quite
firmly. They should stop at least 1/16" above the surface of
the white keys, the thickness of one penny.

Lift some white keys above their normal resting position.
They should return promptly to their original position. Now
hold a key firmly and try to move it backwards and
forwards. There should be no free play at all in this
direction. Check for play to the left and right. There should
be some, but not enough to allow the keys to touch each
other. Slap some of the black keys to their right and left,
and see if you can hear them hitting the adjacent notes.

Press down a note softly while looking straight down at the
hammer. It should be squarely under all three strings. It is
all right for it to be slightly to the right of center, as long as
it is clear that the string on the left will be solidly struck.
Examine the grooves on the hammers, and the shape of
the hammer heads. There should be no deep grooves,
and the surface should not be flat. A groove as deep as
the thickness of a string would be unacceptable for
concert purposes. In the treble the grooves should not be
longer than 1/8". From about A-440 down, they may be
longer.

After checking for squeaks (check the damper pedal
particularly for rapid lifting, and the soft pedal when
pressed slowly), depress the damper pedal very slowly,
and watch the dampers. There should be some free play
before the dampers start to rise, but after the pedal has
been about 1/4" they should start to rise quite uniformly.
Next, observe a hammer and a damper as you press a
key down slowly. The damper should start to lift when the
hammer is about half way to the string. When the note is
held down, try lifting the damper higher with the fingers.
The free play here should be very small. If it possible to lift
the damper more than 1/8", the damper stop rail needs
adjustment. Play a series of loud staccato chords and
listen for notes that do not disappear rapidly enough.
Finally, with the soft pedal down, damp the middle and
right strings with a rubber eraser. Now play the note. Only
a thud should be heard, no sustained sound.

Middle pedals are almost always out of order, and they
are the least important of all the piano's various
regulations. Play a chord in the bass, and while holding it,
push down the middle pedal. Release the keys and the
chord should remain sustained. After trying several
different chords, press down the damper pedal, and while
holding it down, press down the middle pedal. Now hold
down the middle pedal while releasing the damper pedal,
and watch the dampers. None of them should drop. Now
release the middle pedal and push it down again. While
holding it, play notes all over the keyboard loudly. None of
them should be sustained by the pedal.