Jon Page wrote: > I though it was 'figured out' or at least 'arrived at a reasonable > explanation' > for the reason for the uneven pitch changes between registers. Not being > a scaling maven by any stretch but what I gathered from previous > discussions; > it is the % of Breaking Strain induced by the scale design which causes > this instability. The break% change across struts is what's responsible for the differences in pitch response with humidity change there. Low break% is also responsible for the reactivity of the low tenor. As usual, the discussion is already talking about a half dozen different things as if they were all one. As to how pianos go out of tune, in general, with humidity changes, there's not much to indicate that soundboard rise and fall has much part in the process. There is empirical evidence that the bridge cap is a more major player than we suspected, but likely still not enough to account for what we hear. I think the pinblock is also a player, but the one I'm liking more and more is Michael Jorgensen's suggestion. A vibrating string, demonstrably, sounds at a lower pitch with lossy terminations than it does with rigid ones. That would mean that a typically high compression soundboard, though it won't rise enough to appreciably affect the tension of the string, will stiffen under constraint of the ribs and become a less lossy termination of the strings (via the bridge). That would make the strings sound at a higher pitch without significant geometry changes. How it reacts with strings at different break%s, I don't know. I hope to set up some reasonably sensible experiments some day to see if I can clarify any of this. But for now, It ain't the soundboard rising and falling that's changing the string tensions enough to produce the tuning changes we see seasonally. There is still a lot pending. Ron N
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