Blaine Hebert's comment regarding my Zen Archery blog came in an email yesterday before I realized that there was no place for comments. I called him in response and we talked for an hour on a range of loosely related piano tech topics and then decided to make the discussion public. I asked him if he might restate his comment to open tonight's blog and later, Blaine emailed me the following more detailed phrasing of his observation:
"My original question (we wandered around quite a bit) was who has discussed the effect of unbalanced or angled hammers (canted, usually in the bass and tenor) which hit at different places depending on the force of the blow. I am specifically thinking of numerous Steinway grands, some of which will actually miss a string in a hard blow, but hit squarely when played softly. This doesn't seem to be a rare phenomenon, but it requires a good high speed camera to document. Poor traveling can be one cause, but canted hammers tend to be inherently misaligned to their center of mass and hit at different spots depending on the blow. Enough force should twist the hammer enough to break the shank or at least stress the flange or birdseye and glue joint." - Blaine Hebert
I'm not sure who may have spoken on this phenomenon, but I once heard Roger Jolly make an acute and complicating suggestion, that the far shoulder of a flared hammer by traveling further from the center than the near shoulder places a degree more stress on its side of a vertically squared hammer, having effectively more weight, and also more speed and acceleration. Thanks, Roger. I think the idea of the mass of the hammer balanced in opposition to the force that's driving it would neutralize that phenomenon, but would it require a hammer slightly tilted at strike to keep its balance? Is it a different proposition in different locations during its travel due to the changing pull of gravity and other factors? Physics geeks?
I believe that vertical travel is the strongest, the simplest, and the fastest delivery route, with the best chance for a direct hit and a straight-back bounce. Bass-heading travel with a treble-leaning hammer, or vice versa, would exacerbate a weakness due to tilting. And loose pinning would definitely exaggerate the effect, particularly with cloth bushings. Grain, density, and stiffness of the shank could also play a part. If the hammer in a hard blow is turning as it travels, from its direct soft-blow address of the strings to a position a third-unison removed or more, it would not only be missing a string, but the two that it hit (having been carefully fit with no motion...) would have different moments of impact. And presumably such a loose flying hammer would bounce weirdly and hit in a randomly different spot and way, if the note was being repeated.
In my experience, modern Steinways have loose hammer center pinning as one of their features. Also, there is a tradition of tilting hammers in the bass and tenor for reasons of clearance, although I'm not sure that Steinway subscribes to that. In my own work, I have yet to find a clearance problem with Steinway hammers being squared to vertical at strike. In fact, it not only doesn't threaten clearance, but it also helps key-to-whippen-to-knuckle spacing and reduces the degree of double bending needed at the backcheck wires.
To conclude, energy is wasted in the hammer-missing-a-string-on-a-hard-blow scenario. Control is lost to the player. Potential for good tone, power, and repetition is challenged. Hard bushings can offer more stability than cloth with less pinning friction (teflon had that as a merit, when other factors were in balance) and composite shanks are stiffer and more consistent one to the next than wooden shanks. But if there is a hammer balance and shank travel mismatch, losses will result regardless of materials. If hammers are canted, travel should at least follow the cant, string "level" be perpendicular to the travel, and surface of hammers be square looking from shoulders over crowns.
But really, in the extreme situation Blaine describes, the miscreants should be repinned, properly filed, traveled to vertical, squared to vertical at strike, and fit to strings by lifting strings (not left underlifted or overlifted). And good pay should accompany this useful work, because it would make a significant improvement, regardless of fine-detail variables.
As in the phone conversation I had with Blaine, however, we've touched on numbers of subjects that come into play with this changing-travel-by-force-applied syndrome and under-focused on the main theme of Blaine's first email (the posted comment): "the effects of hammer travel to tone and voicing". This kind of force-regulated side travel entirely undermines the normal parameters of tone and voicing. The goals of good tone and dynamic control are enhanced by firm-ish pinning and vertical set-up in the action. But in the situation of wandering side travel, they are literally moving targets. Sorting out and simplifying the variables to the minimum possible is what my logic runs to for firm ground. We cannot voice the complexities generated by this situation. The Zen archer would wait. And we should wait to voice until the foundation is firmed up and the target consolidated into having a bullseye to even aim at.
And then we can begin a conversation about (mechanical) tolerance and the relationship of "hammer travel to tone and voicing". This amount of side travel is clearly out of tolerance. The word that comes to mind on behalf of the piano owner, the piano player, the piano listener, and the piano's poor piano technician, is intolerable!