Bernard writes: << the energy of the hammer returned to the backcheck and the energy of the key to the keyframe become synchronous with the said 2 milimeters. If this two blows are synchronized, there is a higher pulse wave running through the instrument giving more additional energy to the string than when this two blows are time offset (and may cause phase losses when reaching the string).<< Greetings, According to Anders Askenfelt, the timing of these two events is dependant on the force of the blow, so their synchronization is variable. In the publication "Five Lectures", (http://www.speech.kth.se/music/5_lectures/) it is pretty clear that the hammer will return to the back check well after the key has hit the bottom of its stroke on all but the softest blows. The stronger the blow, the earlier the key bottoms in relation to everything else. There are transient pulses that do travel back and forth through the action as the hammer goes through its arc, but without contacting anything, the backcheck seems to be isolated until after escapement. I am not convinced that the distance from the tail of the hammer is as important as the interfacing angle of tail to backcheck surface. There is certainly a feeling of contact when the tail is grabbed suddenly by an acutely angled backcheck as opposed to the longer path the tail makes when contacting a more parallel surface of the backcheck. This seems to be no greater than the differences that can be felt with different hardness of key end felt under the damper levers, though. Regards, Ed Foote RPT http://www.uk-piano.org/edfoote/index.html www.uk-piano.org/edfoote/well_tempered_piano.html
This PTG archive page provided courtesy of Moy Piano Service, LLC