Found it ... I typed it out in October of 2000
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What Pianists Should Know About Pianos
(from the PT Journal, March, 1975)
(copyright 1973, Anton Kuerti)
by Anton Kuerti
Intro:
Anton Kuerti has an understanding of piano mechanism, which, while no means
unique among pianists, is certainly rare.
In its original form, this article appeared in _Clavier_ for May-June,
1973, and was intended primarily to be read by pianists. The version that
we publish here is the author's own revision of the original, made with the
readers of the _Piano Technician's Journal_ particularly in mind.
We think this article has value for our readers, many of whom will find it
technically instructive. Even those who have nothing to learn from it
technically should surely gain from the opportunity to see the grand piano
through the eyes of the author, who is not only an accomplished artist, but
who also knows exactly what goes on inside the piano.
Mr. Kuerti was born in Vienna, but grew up and received his musical
education in the United States. He is a graduate of the Cleveland
Institute, where his teacher was Arthur Loesser, and later studied with
Rudolf Serkin at Curtis Institute. His concert tours have taken him to 18
countries, and he has made solo appearances with major orchestras on this
continent and abroad. Since 1965 he has been on the Faculty of Music,
University of Toronto, where he is artist in residence.
Note the author's strongly expressed views about teflon bushings. While we
do not endorse these views, we do endorse his invitation to readers to
express themselves about teflon by using the survey coupon.
--Don. S. Galt, Technical Editor
* * *
I. Pianos Need Frequent Regulating
Most people are aware of the need to tune pianos regularly. What they often
do not realize, unfortunately, is that tuning is only one 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 especially 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 pianist's requests are usually just a desperate attempt
to restore these standard, reasonable norms.
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.
II. Absolute Evenness Essential
It is a pity that we pianists are so dependent on the perfect alignment of
a fairly complex piece of machinery. The special nature of the piano as an
instrument in which there is no direct contact between the player and the
source of the vibrations makes it particularly important to control the
hammers with the greatest possible sensitivity. The piano cannot make a
crescendo, except by the illusion of a series of very subtly differentiated
notes, each one ever so slightly louder than the preceding one. The piano
can hardly vary the color of sound except by varying the speed of each
thrown hammer and by creating fine distinctions in the intensity of
different notes of the same chord. When playing softly, pianists must often
come dangerously close to the point at which the hammers may fail to hit
the strings, thus causing an embarrassing void where there should have been
a sound. These are some of the reasons why it is so imperative that each
key should respond in an absolutely even and predictable manner.
III. The Author's Credentials
Before continuing, I should perhaps present my credentials for writing
about how to regulate pianos, rather than how to play them, since it is the
latter, not the former, by which I earn my living.
Ever since my family first purchased a grand piano, when I was about ten
years old, I have been fascinated by the mechanics of the instrument and
its inner workings. I watched our tuner take out the action and started
asking questions. Soon, with the spirit of a young boy taking apart a
watch, i started to experiment myself. On my first attempt the tuner had to
return to replace a hammer I had broken when pulling out the action!
Since then, I have continued questioning hundreds of piano tuners and
technicians I have met during my concert tours in many countries, learning
from most of them and eventually sharing my knowledge with some of them. My
experiments also continued, together with the reading of whatever books I
could find on the subject. I regulate my own concert pianos, which I often
take on tour with me. Many pianists and technicians consider them to be
some of the best regulated instruments they have ever encountered.
Currently I own a Hamburg Steinway, a Boesendorfer, and an August Foerster,
all concert grands.
If one demands a great deal from an instrument, one must understand
something about it and know how to communicate intelligently with piano
tuners and technicians. It is not sufficient to say that a piano seems
light, or heavy, when in fact this ailment could be for any number of
reasons. It is comparable to telling a doctor that you feel sick, which
will hardly enable him to help you, short of a complete physical check-up.
That, like a complete overhaul of a piano, is time-consuming and expensive.
Tuners, like doctors, are overworked and most of them are hesitant to urge
people to spend money on regulating, because it might seem as though they
were merely trying to create work for themselves. Therefore it is
worthwhile, and not difficult, for all serious pianists to learn to
diagnose the principal symptoms of maladjusted pianos. The study that
follows refers only to grand pianos; the measurements given cannot be
applied to uprights or spinets.
IV. How the Action Functions
The essential point of the piano action is that it permits the key to push
the hammer toward the string until it is about to strike, at which moment
the connection between key and hammer is interrupted, allowing the hammer
to swing freely, hit the string, rebound, and be caught in such a manner
that it can be played again immediately.
When the jack has pushed the knuckle up to the point where the hammer is
almost touching the string, the horizontal part of the jack is caught by a
felt regulating button, causing the jack to rotate and slide out from
underneath the knuckle. Thereafter the hammer flies on up to the string
with its own momentum, rebounds, and is caught by the backcheck. The
slipping out of the jack from under the knuckle is known as either
escapement or let-off.
V. Striking Distance and Let-off
Two of the most critical adjustments that can be made to the action are the
regulation of the striking distance (or hammer travel), which is the
distance the hammer traverses from its resting point until it hits the
string, and of the let-off (the exact point during the hammer's journey at
which the jack escapes from underneath the knuckle.)
There should be a ratio of just under 5 to 1 between the distance the
hammer moves and the distance the key moves. If the hammers are resting too
low, the ratio will be too large and the hammers will have to be lifted
over a greater distance, causing the touch to feel too heavy. If the
hammers are resting too high, the ratio will be smaller and the striking
distance shorter. Because less "work" is involved in lifting the hammer,
the touch will seem lighter. The pianist's fingers, though, may feel weak,
for there will be less leverage and not enough contact distance to allow
the hammer to be sufficiently accelerated to strike a loud blow. Contact
distance is my term for that part of the key's motion during which power is
being transferred to the hammer. After the let-off point is reached, the
key is out of contact with the hammer; the rest of the key's motion until
it hits bottom is called the aftertouch.
The ideal striking distance is about 1 3/4 inches. Manufacturers'
recommendations vary between 44 millimeters (just under 1 3/4") and 1 7/8
inches. The individual will make a choice in this range, depending on
whether slightly more or slightly less aftertouch is desired. (The closer
the hammers sit to the string, the greater the aftertouch.)
The let-off should occur when the hammer is 1/16 inch (the thickness of a
penny) from the string. To observe the let-off, press the key down very
slowly and note exactly where the hammer stops moving upwards and starts
falling back down. That is the let-off point.
The closer the let-off point is to the string, the more precisely the
pianist can control very soft blows. If the adjustment should get too close
to the string, the hammer may fail to let off at all; it will block against
the string and make the note unusable. If a piano can be regulated only
infrequently and if it is subject to considerable fluctuations of
temperature and humidity, it would be reasonable to have the let-off a
little further from the string, say 1/8 inch, the thickness of two pennies.
For reasons too complex to go into here (involving another adjustment, the
drop), this lower let-off point may also make the slipping out of the jack
function more smoothly and with less friction. Anything more than 1/8 inch
between the let-off point and string, however, will make sensitive control
of soft dynamic levels impossible, for one would then be throwing the
hammer across a large gap where it is no longer in contact with the key. To
grasp the principle involved, imagine that you are throwing a tennis ball
upward, trying to hit a ceiling gently. The closer your hand can approach
the ceiling before letting go of the ball, the more accurately you can
judge the minimum push needed to hit the ceiling.
VI. Touch Depth
There is a complex interlocking of the various adjustments of the piano
action, for the striking distance and the let-off are not only mutually
dependent, they are also related to the touch depth. The touch depth should
be 3/8 inch or slightly more, up to almost 7/16 inch for concert grands.
One flaw that I have seen repeatedly on professionally rebuilt pianos is
that of the black keys' "burying". They must hit bottom at least 1/16 inch
-- the thickness of a penny -- above the resting position of the white keys.
The relative adjustment of these three factors -- striking distance,
let-off, and touch depth -- determines the aftertouch, the free motion in
the key after the point has passed at which the jack has slipped out. If
the key strikes bottom before the jack has slipped out, there will be no
aftertouch. This may be caused by excessive striking distance, insufficient
touch depth, or a combination of the two. To control the hammers well with
no aftertouch one has to play all the way to the bottom of the keys. This
makes leggiero playing impossible, is hard on the fingers, allows the
thumping of the keys against the keybed to be heard excessively, and causes
the action to feel heavy.
If, on the other hand, the striking distance is too small, or the let-off
occurs too early, or the touch depth is too great, there will be a
considerable amount of aftertouch, which will reduce the contact distance
and thereby the power of the blow. Excessive aftertouch also wastes finger
motion, affects the ability of the instrument to repeat rapidly, and makes
it difficult to control volume.
VII. Points of Friction
Together with incorrect adjustment of the striking distance and the
let-off, the most common ailment afflicting neglected pianos is excessive
friction. Friction should be kept to a minimum, and the main resistance of
the key to being pushed down should be the weight of the hammer. Even at
best, friction will be responsible for a considerable portion of the 50
grams resistance offered by the key of the normal piano. If the friction is
excessive, the action will feel sluggish, unresponsive, heavy, and slow.
Friction is mainly located in the action centers. The most important
centers are those connecting the hammer shanks with their flanges, but
there are five other centers that move every time a key is struck: one on
the jack, one connecting the wippen to its flange, one on the repetition
lever, and two (or more) in the damper action.
The usual problem with the centers is tightness, caused by humidity and
corrosion. The simplest way to test for tight centers is to check the key
weighting. The standard weighting for a piano is about 50 grams, which is
just under two ounces. Two ounces, about 57 grams, is still acceptable.
Over 60 grams is distinctly heavy. Less than 45 grams will mean poor
repetition, particularly on concert grands with their long keys. The weight
is judged by lifting the dampers with the pedal and putting weights gently
on the very front edge of the key. If there is excessive friction in the
centers, it will take too much weight to move the key. You may even get a
reading of 80 grams or more. It is rare to find pianos that are incorrectly
weighted, so such a reading probably indicates friction rather than
incorrect weight balance. Most pianos are weighted a little heavier in the
bass than in the treble.
To check whether a heavy action is caused by friction rather than by faulty
weight balance, press a key softly, release it suddenly, and watch whether
the hammer bounces. It should bounce up clearly from rest position before
finally coming to a stop.
A more reliable diagnosis of action friction can be obtained by measuring
how much weight a depressed key will lift up when released. This upward
pressure, crucial for good repetition, should be at least 20 grams (the
weight of 6 or preferably 7 pennies.)[1] The difference between the weight
needed to depress the key (ideally 50 grams) and the weight the key will
lift (ideally 23 grams) is the amount of force needed to overcome friction.
If this difference is more than 35 grams (11 pennies), the friction is
excessive. To confirm the diagnosis, unscrew a hammer, hold the flange in
one hand, and bring the hammer head to a horizontal position. Drop it, and
watch it swing. If should make five or six swings before coming to a stop.
Of course, the heavier hammer heads in the bass will swing a bit longer.
The other commonly used test is to hold the flange horizontally with the
weight of its screw on it. It should drop very freely by itself. Test the
wippen flanges the same way.
Incorrect weighting _can_ result from hammer replacement. For every gram of
difference in the weight of the new hammer there will be a difference of
about five grams in key weight.
VIII. Teflon Bushings
A special problem has been created by the U.S. Steinway company's use of
teflon bushings for the past ten years or so. I have almost never seen a
piano with teflon bushings whose centers are satisfactory, meaning even and
free but not loose. While the felt bushings used by other manufacturers and
still used by the Steinway company in Germany can be treated in various
ways [2] to make them less tight, teflon bushings can scarcely be affected
by any treatment. If too tight, the centers can be reamed and fitted with
larger center pins, but this is time-consuming, expensive, and unless done
by a top expert the chances are that the results will be uneven.
Furthermore, I have found that even after this difficult and time-consuming
job has been done perfectly, restoring the weighting of the keys to normal,
the same problem of tight bushings may arrive again in a matter of days. I
could scarcely believe this when it occurred, but I checked the friction
carefully with weights immediately after the job was done and two days
later; there was a distinct difference, which was definitely due to the
bushings having become tighter.
I have rarely met a piano technician who likes plastic bushings, and I
would not buy a piano that uses them. Owners of new Steinways whose centers
are tight should pressure their dealers to correct them. I have seen
brand-new Steinways whose hammers will just barely drop down to rest
position. Rumor has it that Steinway will soon return to felt bushings.
As my previous comments on this subject have aroused considerable
controversy -- and I am delighted by this -- I would like to emphasize that
I am by no means opposed to progress in piano construction and design;
indeed, I would welcome experimentation with different materials for
various components, especially the hammers. In the case of teflon bushings,
however, I think it is by now clear that they are a misguided construction
economy which only causes grief to piano owners and users who want the
highest quality. Even when teflon bushings are in the best possible
adjustment, they are never perfectly even in response, as felt bushings can
be. There is usually one point in the swing where the plastic has
considerably more friction against the center than elsewhere.
There is a kind of teflon bushing quite different from the type used by the
Steinway company, and which seems to work somewhat better -- although I
would still not recommend it. In this design, the plastic is enclosed in a
small brass ring which apparently prevents pressures in the wood from being
transferred to the plastic and thus making the bushing tight. One would
suspect that the additional expense of this construction would probably
eliminate the economic advantage compared to felt bushings, and since the
latter are, in any event, preferable, I wish all piano manufacturers would
return to the use of felt, at least until a wholly satisfactory substitute
has been devised.
I have found a great deal of concern about this issue among technicians
throughout North America. Many feel that this is a design feature which may
perhaps save the manufacturer some money but at the same time provides the
technician with no end of headaches and complaints. Since my comments have
been attacked in the pages of this _Journal_, and my integrity questioned,
I would like to ask all the readers of these pages who have had experience
with teflon bushings -- positive or negative -- to fill out the coupon and
mail it as soon as possible to Mr. Richard Chenoweth, president of the
Reading-Lancaster Chapter of PTG. Mr. Chenoweth will prepare a resumé of
the results of this poll, which will be printed in a future issue of the
_Journal_. This way it will be possible to say with authority how the piano
technicians who must contend with these problems in the field feel about
this matter.
When teflon centers are not too tight they are often too loose! Loose
centers can be detected by the clicking sound they cause when a note is
played. If a hammer can be moved distinctly from left to right, and if the
swing tests mentioned above show it to be swinging back and forth like a
pendulum eight or nine times, then the center is too loose.
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Footnotes:
[1] Pennies weight 3.2 grams each.
[2] The traditional method is to moisten the centers with a mixture of 1/3
water and 2/3 alcohol. I have recently switched to using a spray lubricant
called "WD-40" , which works instantly, does not cause the felt to
deteriorate, and is unlikely to make the centers too loose. If the centers
are extremely tight, it may still be necessary to apply water and alcohol.
After application the centers become still tighter temporarily, and the
desired effect does not take place for an hour or so.
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at the time I wrote: --- part II to follow. I wonder how long Anton used
WD-40 (!) and what the long term effect on his pianos was! --s
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