The zen archer must know the bullseye of the target. Similarly, a piano technician will benefit by aiming work at a clearly understood target. Here is grand regulation's bullseye:
Each hammer travels vertically and addresses its string(s) as if it were balanced on its shank, i.e., its mass is directly above the force that is driving it (a hammer balanced on its shank at strike is in its strongest, most stable disposition). The action sits fully bedded on a keybed that is horizontal, and the index for both vertical and horizontal is gravity. (If the piano has not been leveled, substitute keybed as the index.) The bore distance has the travel arc of the crown arrive so that the hammer molding (if viewed from the side) is at right angles to the string as it strikes. And each hammer contacts all of its unison strings in the same moment of impact, with the piano at pitch and in tune, and with the hammer's strike at the optimum location for tone production.
And: the regulation for each note is balanced to produce adequate and expected clearances, support, friction and lack of friction, spring tension, distances, stops, and follow through. Add to these, please, appropriate weight, inertia, and transfer of energy. And ideally, action parts should offer appropriate grain orientation, surface finish, nap direction, compression/tension of materials, center freedom/stability, and alignment. The details of this balance (balance because the favoring of one consideration over another may diminish the overall performance, stability, wearability, noise, consistency, longevity, and so forth) should all be in place for hitting the full potential of the bullseye.
Greatest simplicity is the essence of the bullseye. If the vertical axis of the bullseye hammer is tipped in any direction, it complicates strike, energy transfer, and bounce (tone, power, and repetition - TPR). Taken in its simplest terms, vertical address and full fit at strike, at pitch, and in tune are symptoms of hitting it.
The many parts, the range and interaction of materials, the vectors of motion, the geometry, physics, chemistry, and general math behind what happens, the intent-to-actuation variables, the limits to resources, the human implementation, the taste, artistry, and skill, all the too many factors make analysis overwhelming. And the words to describe them become denser the harder they try to be precise. So. OK. A grand piano presents a cornucopia of complexity.
But maybe a trite maxim can help. KISS (keep it simple, stupid), for instance, applied in small step-by-step increments, is just sensible. If each step is clear and simple, and the steps are taken in the simplest order, if the references that inform and validate each step are correctly related to the appropriate index, if the work goes with the nature of the materials, if the tolerance set for each step is both demanding enough and simple enough: a lot of ifs. But I have found, in the development of my Grandwork™ tools and protocols, that it's doable.
Accumulated error is our adversary. In subsequent postings, I will show how these tools and protocols combine to provide accumulated accuracy.
But I'll leave, for now, with one example of a built-in challenge to our ending in the bullseye and a quick summary of why it might be important to think this through with me.
Steinway plates, in particular, are bowed from side-to-side, with a symptom showing up most clearly in the high treble. String heights declining there mean that in each set of three strings (each unison), the bass side string is lifted just enough to be stable (not underlifted), the middle string is pulled slightly further, and the treble string is pulled enough to complete the fit but not to be overlifted. We need each set of unison strings to be set in simultaneous motion by its hammer, those strings to be parallel to the keybed at strike, and each well-filed hammer to be vertical as it strikes. Clearly this is a tall order.
It can be done, if each step leading up to the fit is spot-on. If the fit is not accomplished in these terms, however, one or more of a variety pack of problems will be the outcome: hammer misfiled, hammer not hitting all three strings together, angle of hammer at strike off, angle of bounce off, one or more overlifted or underlifted strings, and so forth.
And here's the rub. Our best tuning and our best voicing will not only not correct such errors, but the needles, additives, and other remedies we apply will likely complicate the situation. We will be moving further from the target we've missed, with the options we have left. Just when we should be perfecting and polishing, we're complicating, dulling down, out of time, and out of money.
The goal of the simplest outcome is best achieved in simple increments along the way. By the time we encounter the collateral complications of not following this path, it's simply too far, too hard, and too expensive to get it back...