Hi, 

I had the opportunity to exchange emails with Mr. Kuerti some years ago. He has, of course, abandoned WD 40 and graphite in his treatment of pianos.

Susan thanks for typing this in. I thought it might be more useful as an attached file in .rtf format.

Regards, Don Rose

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

Part II of Anton Kuerti's article, "What Pianists Should Know About Pianos."

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IX. Knuckles

Another important friction point is the knuckle. As you start to depress the key, the knuckle rubs against the repetition lever, and as the jack slips out near the end of the blow, the jack also rubs against the knuckle. The knuckle is normally lubricated with dry graphite, soapstone, or unscented talcum powder. Some technicians believe it is harmful to apply graphite directly to the knuckle, and it may be that it does contribute to hardening the knuckle, which in turn may cause the note to "bubble" or repeat unintentionally by bouncing on the jack. I have recently switched from using graphite to using WD-40, [!!@$@#&!#!] previously mentioned in connection with freeing sticky centers. It also works wonders lubricating key bushings and other action parts.

To judge whether there is too much friction at the knuckle, press a key down very slowly and listen for any creaking or rubbing sound. If you hear any, lubrication is needed. Wear can cause excessive friction, for once the knuckles lose their round shape the jacks will not slide easily. Worn knuckles can sometimes be improved by brushing them up with a wire brush, or by reshaping them with a sandpaper file.

X. Key Friction

Several other minor friction points that need occasional lubrication are the top of the capstan, the jack regulating button, the leather below the drop screw, and the spring groove. However there is a much more important source of friction, and one that is often overlooked, particularly in new instruments: the key bushings, and especially the hole in the key where it rests on the balance rail. If the bottom of this hole is too tight, the motion of the key, particularly on its rebound, will be sluggish. (This is often the case with new or seldom played instruments.) On the other hand, if the hole becomes too large, the keys will rattle.

To test for friction in the keys, lift the keys up above their usual position. If they remain in the lifted position, the center rail pin holes need to be very slightly enlarged. This is done simply by gentle pressure with a round tool, like an awl, not by using a sharp edge to remove wood. There should be no play backwards and forwards in the key. At the front rail pin there should be no friction at all. The keys should not, however, be able to move excessively from side to side, since that would create unpleasant slapping noises. If, when slapping some of the keys (particularly the black ones) to the left or right, you hear a clattering noise, either the front rail pins need adjustment or the key bushings have become too worn. The front rail pins are slightly elliptical and can be turned with a special tool in order to adjust the amount of lateral play in the keys. Remember, however, that after the pins have been turned to reduce this lateral play, wear will be more rapid than previously because the key bushings will be rubbing against the narrower sides of the front rail pins.

XI. Extraneous Noises

Aside from loose centers, unpleasant clicks can come from several other sources. Loose hammer heads are a common cause, especially in dry climates. A pronounced clicking at the extremes of the keyboard may result if the key blocks that hold the action down against the keybed at either end of the keyboard are not secure enough. Generally there are some strips of paper glued to the bottom of these blocks, and they can be removed to make a tighter grip.

A persistent clicking or wooden knocking may be caused by a warped action or improperly adjusted center rail studs. The action is held down in front by the key blocks; in the rear it slides under some wooden guides that hold it down. The center rail studs are in the middle, so if you screw them down to lift the middle of the action along the center rail, you are bending the action frame and may cause it to warp. Any change in the height of the center rail studs will also mean a change in the touch depth, for by raising the center rail you are also raising the keys that are lying on it. This is sometimes a practical and effective way to temporarily correct the touch depth in an emergency, but it is a poor idea under normal circumstances. Touch depth is properly adjusted by either removing or inserting paper punchings under the keys. The let-off and striking distance are also slightly affected by changes in the center rail stud settings.

XII. Additional Adjustments

Quite a number of other action adjustments can be made. The position of the jack can be adjusted forward and backward by a regulating button. If it is too far backward, there will be too much friction as it passes under the knuckle. If it is too far forward, there is a danger of missing entirely, in which case one may strike a very hard blow and cause the jack to escape so quickly that no sound is produced at all. When this happens at a concert it is a great catastrophe and embarrassment. I have found a good test which will eliminate the risk of this defect: place one finger on the hammer head and then press down hard on the corresponding key. If the jack slips out, it is too far forward.

The height of the jack relative to the repetition lever can be adjusted; this has an effect on the amount of friction in the action, on its rapidity of response, and on repetition. To test this, gently depress the jack under the regulating button with a finger; the hammer head should move almost imperceptibly, and the jack must be able to return to its original position rapidly and without rubbing against the knuckles. This can easily be felt by the finger.

More important, and easier to judge, are three other adjustments: the strength of the repetition springs, the setting of the drop screws, and the position of the back-checks.

The repetition spring pushes up the repetition lever, which lifts up the knuckle -- and thus the hammer shank -- so that the jack can slip back under the knuckle in preparation for the next blow. On most pianos, this spring does double duty: it also pulls the jack back. If the spring is too heavy the action will feel heavy and jerky. If it does not have enough tension, the repetition will be sluggish. Here there is room for personal differences. The pianist who wants to stun his audience with extremely rapid repeated notes and trills will want a stronger spring than one who wants above all to have perfect dynamic response at the softest levels of playing. To judge the spring tension, strike a moderate blow, and then release the key “very” slowly, watching the hammer. It should rise distinctly, but without a pronounced jerk which can be felt in the key.

Some instruments, including the Steinway, have no screw adjustment for the repetition spring tension, which means that adjusting the springs becomes a tedious, difficult, and approximate task. Each spring must be individually bent and then replaced in its slot. This feature is unfortunate, because, as hammers are worn and sanded, a lighter spring adjustment is needed.

After the jack has escaped (the let-off point), the hammer head drops. This is known simply as the drop. The drop adjustment can affect repetition, heaviness, and evenness. It should drop 1/16" to 1/8" below the let-off point.

The back-checks catch the hammers after a blow, to keep them from bouncing back and forth. On very soft blows the hammers usually do not catch against the back-checks; if hammers do not catch on medium blows, the back-checks are out of order. Excessively strong repetition springs can also prevent the back-checks from catching properly. The back-checks are adjusted simply by bending the wire that attaches them to the key. Improperly adjusted back-checks and repetition springs may cause keys to repeat unintentionally, or to fail to repeat when intended! The hammers should be caught as high as possible, no more than 5/8" from the string. However, they must be inspected carefully to insure that they do not rub against the heel of the hammer as the hammer travels upward. To check this, use a test similar to the one for the correct position of the jack under knuckle: place one finger on the hammerhead and another on the key, and rock back and forth. There must be no rubbing felt or heard. The heel of the hammer must be rough and free of any greasy material. It and the back-check can be roughed up with coarse sandpaper.

Another adjustment of some importance is the point at which the dampers start to lift. If they move before the hammer is about half way on its travel to the string, the action will feel sluggish, for the extra weight of the damper is added before the key has received enough momentum. Short crisp staccato will also be difficult, because the damper will not touch the string until the key is almost at rest.

As usual, there is another side to the coin. If the dampers lift too late, legato playing will be impaired, for the dampers will stop the sound as soon as you start to release the keys. With dampers lifting too late it is also possible that the hammers will strike the V-shaped dampers in the bass rather than the strings, or they may strike the strings before the dampers are completely clear of the strings, producing a dull and muffled sound which will not sustain. The dampers should lift simultaneously, and the pedal should have no more than 1/4" free motion before it starts to lift the dampers.

XIII. The Question of Voicing

Sound quality is mainly determined by the quality, shape, and hardness of the piano's hammers. Most manufacturers put some hardening solution on the hammers, particularly in the treble section, to achieve greater brilliance. Another way to harden the hammers is by using a specially shaped hot iron. 

Applying a hardening solution is dangerous; it may make the hammers too hard and cause them to sound metallic, but it is sometimes useful and necessary when hammers are much too soft.

The treatment and voicing of hammers is the most controversial question relating to pianos, and the answer is partly governed by matters of personal taste and by the type of use intended for a particular instrument. A piano used mainly for chamber music or accompanying should be less bright than one used for solo recitals. A piano for playing a Rachmaninoff concerto with a big symphony orchestra must be voiced so brilliantly that it may well sound harsh and explosive when used in a small studio. In the case of my own instruments, which are rather brilliantly voiced, I always keep them completely closed when they are in my home or studio, with the music rack resting on top of the case. This makes the sound very pleasant, saves the ears from unnecessary abuse, and helps protect the inside of the piano from dust and rust.

To achieve a clear and pure sound, the hammer heads must be kept round or pear-shaped by frequent sanding and reshaping. As soon as grooves in the felt become too deep or too long, the sound becomes distorted and coarse. The grooves in the treble should not be more than 1/8" long. Those in the middle or lower registers may be longer.

How often one sands the hammers to restore their original rounded shape will depend on financial considerations and on how important it is to be able to create an ideal ringing sound. Hammers on concert pianos kept in New York for artists to use will probably be gently sanded after almost every concert, in order to keep their shape perfect. This means, of course, that the hammers will not last long, and will need replacement every year or two. Obviously it would not make sense to treat a home piano in this manner. Depending on how much use the piano gets, reshaping the hammers every one to five years would be sufficient.

One problem often arises, particularly with neglected pianos whose hammer grooves have become very deep. From repeated compressions of the felt over many years, the small area contacting the string after the hammer has been reshaped is harder than it should be, so the sound becomes too bright and hard. As one removes felt and approaches the hammer's wooden core, the sound will in any case become more brilliant, perhaps harsh. To counteract this, the felt is softened by pushing needles into it. Whenever hammers are reshaped, the felt will undoubtedly need some needling or voicing in order to even out the differences in hardness between different hammers.

Voicing must be done by someone with a very sensitive ear. The quality of each note must be judged, considering both strong and weak blows. If the sound is too hard when struck loudly, the shoulders of the hammer require deep penetration by the needles. If the sound is too hard when a key is struck softly, the hammer requires only surface needling. It is a good idea to start the voicing procedure with the soft pedal depressed, evening out the scale first in this manner and needling only the left and center portions of the hammer. First check to make sure no hammers are hitting the left strings with the una corda depressed. [3] Then continue voicing without the soft pedal, but when you come across a particularly harsh note check with a rubber mute to see if the hardness is being caused more by one side of the hammer than the other.

Most manufacturers recommend that hammer heads not be needled directly on the top surface that strikes the string; needling in that area could create a permanently soft and mushy sound. The practice might be desirable in the case of some home instruments, but it tends to increase the amount of wear and tear on the hammers and to shorten their life. Sometimes it is necessary to needle the striking surface if deep needling the shoulders does not bring about the required effect.

Before voicing make sure all hammers are striking all three strings solidly. After checking the hammer alignment visually, check to make sure the hammer surface is level and touching all the strings equally. This can be done by pushing the jack up without permitting it to slip out, placing the finger firmly against the end of the jack to prevent it from sliding forward, or by pressing it slightly to one side or the other. When the hammer is touching the strings, make sure the damper is lifted and pluck each of the three strings. If one string continues to sound, this means the hammer is not touching it and is not flat. Sand the other part of the hammer accordingly.

A mellower sound quality can result if the hammer surface is gently roughed up with a wire brush, but the effect does not last long.

I feel it is better than an instrument be slightly too bright than too dull. A performer can usually achieve a desired quiet effect even on a brilliant instrument by restraining himself, listening to the level of the sound he is producing and adjusting accordingly. This cannot be done if the sound is too harsh, though, or if the player is unable to refrain from the habit of banging with all his might. Furthermore, a bright-sounding piano has more character in the soft and intermediate dynamic ranges and a wider dynamic range altogether. It is possible to play as softly on a brilliantly voiced instrument as on a dull one, provided that the action is in perfect regulation, but it is not possible to play very brilliantly on a dull piano. In voicing, it is better to err on the side of brilliance because it is always easier to make a piano more dull and mellow. The hardness of hammers that have been excessively needled is not easily restored.

XIV. Vibrations

On certain pianos, especially the Steinway, the sound can also be influenced by the section of the string between the tuning pin and the treble bar.

An overly harsh piano can often be made more mellow by placing a felt strip between the strings just in front of the bar. This felt, however, weakens the character of the sound, because certain very characteristic overtones become suppressed. The same applies to the portion of the string between the bridge and hitch pins.

The treble bar can be a serious problem as the piano gets older; grooves will be formed by the great upward pressure of the strings and their sliding back and forth when the instrument is being tuned. The strings may vibrate against the enlarged grooves, creating distorted and metallic sounds. This problem can sometimes be remedied by moving the strings with a screwdriver slightly to the right or left so that they pass over a different point on the bar.

Unpleasant vibrations on bass strings are usually caused by their windings becoming loose. This can often be corrected by loosening the string, and twisting it several times, hooking it over the hitch pin with as much torque as possible.

Buzzing vibrations are also caused by cracks in the sounding board or by foreign objects lying on it (or on the strings), loose screws in any part of the piano (including the action), loose veneer, or parts of the frame that have come unglued. Some very frequent sources of buzzes are the lock, the stick for holding up the lid, the music rack, the hinged flap of the fallboard, and the fallboard itself.

Often vibrations that seem to come from the piano have their source elsewhere -- windowpanes, objects on the piano, loose moldings or floorboards, picture frames, etc. It is often a long and frustrating two-man task to trace these unpleasant noises.

One more important source of vibrations and poor sound quality is the failure of the strings to press down firmly against the bridge. The amount of downward pressure exerted by the strings is called the bearing, and it is measured by the angle of the change of direction as the strings cross the bridge. This is hard to measure without a special tool, but with some ingenuity and a thin metal ruler to use as a straight-edge one can at least ascertain whether there is some bearing. As pianos age they usually lose their bearing gradually. Correcting this is a major task, except in the case of the new Baldwin SD-10 concert grand, where the bearing can be easily and individually adjusted for each string.

Another factor affecting sound quality is the exact point on the string where the hammer strikes. Moving the action backward or forward even 1/16" can cause a great change, particularly in the treble.

XV. The Condition of the Strings

A piano can sound at its best only when it is well in tune. I do not use the word perfectly, because that is impossible. The art of tuning is not an easy one. There is a proper way of setting the pins, which will help the piano stay in tune better. In order to tune properly, the tuner must strike the piano very hard, even harder than the pianist. The tuning pins are long and can be twisted. If the tuner merely twists them, the instrument will go out of tune immediately. He must make sure that the pins turn before twisting them back slightly so that the direction of their twisting tension is the opposite of the direction from which the string is pulling. Most pianos economize by having the strings pass around the hitch pin and double back, each length of wire thus serving for two strings. This slightly increases the tuning problem, for any adjustment to one string will affect its neighbor. This economy is particularly regrettable when a string breaks during a performance, for it means that two strings will be out of use; the wire, rather than flying away, will stay in place, creating a terrible vibrating racket.

Sound quality is also affected by the condition of the strings. Rusty, old strings sound about the same way they look. A concert piano should be restrung at least once every ten years or so. In between these times it is good to discourage people from touching the strings, or, for that matter, scratching them with foreign objects in search of new, earth-shaking sounds.

XVI. Quality Work Essential

Needless to say, all action adjustments and regulations must be as even as possible. It is crucial that the repetition springs be the same throughout the instrument, that the height of the hammers when the keys are depressed very softly and held down are even (this reflects the drop adjustment), and that the line formed by the caught hammers after sharp blows is fairly straight, etc. It would be possible in some cases to adjust to a consistent standard even if it is one that varies from normal measurements.

If a piano has not been regulated for many years, it is probably wisest to have a complete regulation done by a qualified technician. While it is true that one adjustment does affect the other, it is nevertheless often possible to improve greatly the feel and response of an instrument by correcting one or two of the most serious defects. Some tuners are opposed to working on the action unless the do a complete regulating job, but there is really no reason why tight action centers, incorrect striking distance, or faulty let-off regulation, the three most common defects, should not be individually treated.

I am almost constantly retouching and rechecking the regulation of my instruments, and I think it would be desirable for tuners to do the same when the customer so wishes. Naturally, tuners should be entitled to charge for any regulating done in addition to tuning.

Perhaps concert pianists ought not to assume that piano manufacturers and local concert sponsors can afford to maintain their concert instruments in top condition. (Whether they “can” afford it or not, the fact is that they “don't”.)

All instrumentalists except pianists invest in very expensive instruments, the insurance and repair of which alone may come to more than $1,000 per year. In addition, they are faced with paying the fees and travel expenses of accompanists. (Cellists and bass players must often buy an extra airplane seat for their instruments.) I think that pianists should be willing to spend approximately three to five percent of their fees to help keep pianos in good repair. The alternative seems to be unsatisfactory instruments, unpleasant scenes, and inferior performances, none of which help increase the popularity of either piano concerts or pianos. It would be a small price to pay.

Footnote:
[3] Some people prefer a less drastic change in sound quality, and wish to have the hammer continue to strike all three strings but miss the grooves, thus hitting the strings with softer parts of the felt.