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Joined: May 2001
Posts: 29,165
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Joined: May 2001
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I got this from the NH Pianos website and thought many would find it interesting.

Besides being a terrific pianist, Kuerti is known for being perhaps more knowledgeable than most concert pianists about the inner workings of a piano. When he played at Mannes quite a few years ago I saw him trying out the piano after which he had a discussion with Mannes' tech about what he wanted adjusted in the regulation.

Regulation Checklist

Anton Kuerti's Step-By-Step Guide
for determining if your piano is in good regulation


PIANOS NEED FREQUENT REGULATING(applies to grands only)
Materials needed: 20 pennies, a ruler, a doctor's tongue
depressor or piece of cardboard, a pencil with an eraser. 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.

1.Jack Position and Obvious Defects:
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. note - It is not possible to accurately determine proper regulation of the jack without removing the action from the piano (not recommended). This test will only show profoundly mis-adjusted jacks.

2.Weighting and Friction in Centers
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 dependent on the weight of the felt hammers, excessively low touchweight may be an indication of badly worn hammers.


3.Striking Distance:

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.

4. Let-off and Lubrication:

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.

5.Drop and Aftertouch:

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.

6.Back-checks:

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).

7.Repetition Springs:
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.

8.Touch Depth:
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 concertc 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.

9.Keys:
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.

10.Hammers:
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.

11.Pedals and Dampers:
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.

12. Middle Pedal:
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. To be suitable for concert performances, a piano should pass all the above tests with the possible exception of number 12. Preparation: Remove the music rack and bring a good lamp or flashlight to the piano.

Last edited by pianoloverus; 03/15/12 09:18 AM.
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Just a few thoughts that may be of interest, in no particular order...
As with everything, there are always exceptions to the rules. As an example, if the rep springs are too weak, then you'll struggle to set up the rep lever height, the jack position, blow distance etc. I do rep springs after I'm happy with centre friction.

Personally, I'd recommend doing any hammer filing and travelling, wippen spacing etc before any regulating as such. Same for any key bushing easing. These tasks can involve taking the stack apart, so you want to get them all done before you start regulating. Whilst it's apart, polish the capstans, maybe even the rail pins (but be careful not to mess up the punchings). In fact before all of that, check the key frame is well bedded, and always put in the pin blocks.

Now that I think of it, and how I've learnt over the years, I strongly recommend that no-one who considers themselves to be a 'dabbler' does any of this! If you're really keen to have a go as I was, spend some time with techs, get books, have a go, and accept that you're unlikely to get concert prep results until a few years later at best!

I guess the article gives an interesting overview for those that don't know. I just hope that it doesn't result in many readers accidentally breaking off the outside hammers attempting to remove the action for the first time!



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sorry, just looked again and realised it was a assessment-check list, as opposed to a how-to-regulate check list.
My points stand though.

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Now I can put that jar of pennies to good use.


"Imagine it in all its primatic colorings, its counterpart in our souls - our souls that are great pianos whose strings, of honey and of steel, the divisions of the rainbow set twanging, loosing on the air great novels of adventure!" - William Carlos Williams
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That is a really great list for evaluating the technical condition of a piano. It is a great way for pianists to learn more about their instruments and to be able to communicate clearly with a technician about what they like or don't like.


Moderated by  Ken Knapp, Piano World 

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