Ed Sutton wrote: ------------------------------------- > Probably more productive to think about changes in bridge cap thickness. > Ron Nossaman may be able to send some statistics about his laminated > bridge caps. He also lives in pitch adjustment hell, so may have more > experience to share. > > Ed The bridge cap gets a large part of the blame, but it's not reacting more in one place than another. When the cap thickness changes with humidity, all the strings of a unison will change in length by (nominally) the same amount. That's not the same percentage, the same amount - like 0.001" (arbitrarily). The result will be that the shorter string (overall length) will change pitch more than the longer, with the one in the middle in between. That's it. Where they are at any moment that you happen to measure them depends on the humidity conditions at the last tuning, where the RH has been since, where it is now, and in what direction and at what rate it's changing. You're looking at a snapshot in time of a continually changing dynamic system, most of the dynamics of which are not on your notepad as you ponder what's happening. Pianos having individually tied strings were originally intended to have all the strings the same length overall to combat this effect, so the unisons would stay closer in tune even though the overall pitch would continue to change. And yes, epoxy laminated veneer caps do most definitely improve tuning stability. From pitch adjustment hell, where I tuned five today at 20%RH that were last tuned at 70%+. Trombone time. Ron N
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