Precision action balancing
Touchweight is the term we use to express how much effort it takes to play a piano key. It is a complex issue affected by friction, geometry, inertia and human perception. Simply put it's how heavy or light the action feels to play. We have a great deal of control over these factors and can make a piano action play just the way you like it through touchweight corrections or action rebuilding.
The piano action is comprised of a series of levers that let the player propel the hammer toward the strings at many times the speed at which they depress the keys. Like a playground seesaw the weight on one side of the key affects the effort needed on the opposite side to overcome that weight.
Since its invention 300 years ago the piano has changed dramatically although most of the major improvements were complete before 1900.
There are some very important differences between the action or playing mechanism in older modern pianos and that of today’s pianos that must be considered when rebuilding an older piano action with new replacement parts. The essential differences are that today’s hammers are made heavier to provide greater tonal power and that the leverage has been changed to compensate for the heavier hammers. You can see where problems arise when new heavier hammers are installed on an action without the modern leverage advantage. This problem can be solved if the proper action parts are chosen in order to correct the action leverage. Often the wrong choice is made resulting in an action the plays like a ton of bricks.
Another important factor must be addressed in order to achieve an even touch weight. All new hammers are produced with unevenness in weight from hammer to hammer. As part of making the action feel absolutely even from key to key I remove material from any hammers that are heavier than desired so that from hammer 1 to hammer 88, each hammer decreases in weight in an absolutely smooth curve and each hammer differs from its neighbor by no more than .2 grams.
A third factor in achieving a desirable and even touch weight is key leading. At the factory, lead weights are inserted in the keys in order to lessen the effort needed to depress the keys and to compensate for inconsistencies in leverage and parts.
When new action parts and hammers are installed it is critical that this weighting be rebalanced to compensate for the difference in weight between the new parts and original parts, and to achieve the desired playing resistance or "touchweight". Unfortunately many rebuilders, whose opinion is that the factory weighting was done correctly and should not be altered, skip this vital step. Considering today’s heavier hammers this philosophy often results in an excessively heavy action. Again we must recall the example of the playground seesaw where the weight on one end is reflected directly in the force needed to push down the other end.
When all these factors are correctly addressed the result is what I call a “Precision Balanced Action” that provides the pianist the possibility to hear exactly what his fingers play without the distortion that occurs through inconsistencies in the piano action. This removes what can be a huge distraction and allows the pianist to concentrate solely on playing the music.
registered piano technician