A piano key’s fulcrum, the site of the see-saw action, occurs where the balance rail pin goes through the key. The hole in the bottom of the key should be the same size as the pin going through the hole. If the hole is too large, the key bounces with every return to its rest position. This bounce makes an audible thump and interferes with the enjoyment of the music. When the hole is even larger, the key actually slides forward and back making a click that adds to the action noise.
In extreme cases, routing out the area of the hole and installing a new hardwood plug becomes necessary. In not-so-serious cases, glue sizing can be accomplished to eliminate the thump and click.
As with hammers becoming hard over time, the felt under the keys also becomes packed and hard with time and use. Back rail cloth that is hard makes the return of the keys to their rest position audible. Hard front rail punchings make the bottoming out of the key when it is played create an unwanted sound as well. Replacing these felts can make a major improvement in reducing action noise.
These photos show the contrast between old and new felt.
When a piano key moves from its rest position, felt bushings in a mortise on the underside of the key slide along a pin to guide the key in its up-and-down motion. Over time, the bushing wears and the key acquires excessive side-to-side motion. Key bushings are glued in with water-soluble glue so they can easily be removed and replaced. One of the more frequently overlooked aspects of piano maintenance, key bushings should be replaced when the key movement varies from a well-controlled vertical motion.
These photos show bushings needing to be replaced, steamed and ready to remove, mortise sizing cauls in place, and the new bushings being installed.
Changes in atmospheric humidity is the primary cause of a piano going out of tune. In the upper plains, this can be a major issue. As the soundboard takes on or sheds moisture, the wood changes dimensions. This causes the tension of the strings to change. Thus, the piano changes pitch. Unfortunately, it is rare that these changes of pitch are equal throughout the range of the piano. In most pianos, the octave below Middle C is the most sensitive to humidity changes, and the bass strings below the bass-tenor break the most stable. A piano tuned in August can sound quite dissonant in February.
The Dampp Chaser Corporation has been producing equipment and systems for over half a century that strive to control the environment within a piano. They can be amazingly effective. The enclosed nature of an upright piano responds better than the grand piano, but systems installed in grands are helpful in mitigating extreme changes. A “Piano Life Saver” system won’t eliminate the need for regular tunings, but the string tension changes caused by soundboard and bridge dimensional changes will be smaller.
There are many variations of touch weight. These include, heavy touches, light touches, stiff actions, sluggish actions, fly-away actions, unevenness, and actions that respond as we would like. Friction is necessary, but too much friction in the wrong places causes havoc in a piano action. A grand piano action depends on gravity to function properly, and consequently too much or too little mass in the wrong place means weight added or subtracted to achieve balance and a functioning action. To a lesser degree, the same balancing act is necessary in an upright action. In uprights, springs rather than gravity play a large part in how an action feels and responds. Adjusting spring tensions can make a huge difference in the touch of a piano.
Action geometry is extremely important to a playable action. Over the years, manufacturers have used action parts of various sizes. If action parts are replaced, they must be exactly the right size. The difference of one millimeter can make an enormous difference in function and response. I have seen cases where incorrect parts have been used. In an effort to make the touch weight fall within playable parameters so much lead was added to the key sticks that despite the weigh-off numbers reading correctly, playing was virtually impossible. The problem is inertia. Yes, a washing machine motor can be made to move a freight train, but what an effort! The proper parts must be used, the geometry must be correct, and weights in the keys must be reasonable. High inertia means fast playing becomes difficult if not impossible, and fortissimo is also impossible. It’s simply not possible to make the key accelerate.
The piano sound is produced by a felt-covered “hammer” striking the strings. Every time the hammer hits the string, fibers in the wool are compacted which over time makes the felt hard. Hard felt produces more and higher-pitched harmonics. Also, fibers of the felt are broken and worn away which leaves grooves in the hammers where the hammer comes in contact with the strings. As these grooves grow deeper and longer, the tone becomes less like the clear tone of a bell and more like the thud of a drum. Correcting these changes is called voicing.
Reshaping a hammer to remove grooves and the flat shape that contacts the strings is accomplished by filing away felt to reveal fresh felt and restoring the original shape of the hammer. This makes it possible to restore a clear and pleasant tone to the piano. There is a limit to hammer filing. Eventually it is necessary to start with a new set of hammers. That, however, is usually after many years of use. Good maintenance means regular filing in small increments. Allowing the hammers to become deeply grooved and flat could mean filing is less satisfactory or even impossible.
With the hammer shape restored, manipulating the fibers within the hammer can then be accomplished. Using a variety of technics the compacted fibers deep within the core of the hammer can be softened and a measure of the original resilience of the felt restored. Some hammers, particularly those manufactured in Asia, have chemical additives. Over time and with use, these hammers can become extremely dense and hard which produces a tone equally dense and hard. Overly bright, even harsh. Good voicing can bring the sound of a too-bright piano to a warm, pleasant tone that makes playing and listening to the piano enjoyable and musical.
The opposite of too bright can also be a problem. Occurring more rarely but certainly possible is a set of hammers that does not have enough support or firmness in the right places and the tone is weak, mushy, muted, or unfocused. In most cases this can be corrected as well.
Voicing is an important part of good and regular piano maintenance. To achieve an even and musical voice throughout the entire range of the piano, the piano must be in good regulation and voicing attended to regularly. As with nearly all procedures in piano maintenance, everything is progress toward a goal. Perfection is elusive but over time and with persistence, we can get close.
Stuart D. is by far the best piano tuner/technician I have ever had. His professionalism is only surpassed by his knowledge, experience, musicianship and dedication! In my 55+ years of piano teaching I have probably seen them all and no one touches my piano to tune or repair it except Stuart!
605-880-3770
