Recently I was called by a very accomplished pianist with a fine grand piano with complaints of rubbing noises in the action and uneven touch. I proceeded to address all the usual points of contact and friction --- front rail pins properly aligned, all key pins polished and lubricated and balance holes free of excessive tightness, jacks centered in the balancier window, proper gram-friction and freedom of movement in all the action centers, knuckles impregnated with teflon and wippens coated with Emralon, no rubbing key tails or hammer tails or backchecks, resilient wippen cushions, action/keyframe properly bedded, all screws and parts and rails tightened, etc. You name it and it was corrected! The final result was perhaps one of the quietest and most responsive actions I have ever encountered. And yet, after each step, when the action was re-installed into the piano, the same faint scraping sound and unresponsiveness reappeared.

Only when the stack was removed and just the keyframe and keys were installed in the piano did the true source of the problem become evident. The back-action had been installed ever so slightly off-center in relation to the action, and each time a key was depressed its tail would lightly rub the side of the adjacent damper lever, causing the faint noises and impeding the touch. It also now became obvious that the problem did not exist in the upper treble section, because there are no dampers/levers in this area.

The point I am trying to convey (which I gained through this frustrating experience) is that we often tend to overlook the back-action/damper system when servicing grand actions. It is usually a case of "out of sight, out of mind," and we assume that everything is automatically fine "back there." It should be recognized that the back-action is an integral component of the entire system, one which greatly affects and influences the performance of the action itself.

Rob Eccardt, RPT