<div dir="ltr">It seems that on either grands or uprights, the right string leads the pitch change and moves the farthest. That is, the right string of the unison is the first to rise in the summer and the first to fall in the winter. The left string lags behind and ultimately doesn't change as much.  I don't know why. Albert Lord. <div class="gmail_quote">On Wed, Jul 16, 2008 at 2:18 AM, V T <<a href="mailto:pianovt@yahoo.com">pianovt@yahoo.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Now that we covered the tenor and the low tenor, on to a more irritating stability problem: Unisons that go out with humidity. At first, one might wonder why three strings that are so close together on the bridge would follow independent pitch trajectories when the humidity changes. I did notice that, on my piano, the problem was most objectionable in the low and mid treble, but probably just as present all the way to the top. Speculatively speaking, I think it has to do with the fact that the total string lengths among the three strings are not really equal because of the tuning pin locations. Any thoughts about this? >Most pianos go quite sharp in the summer because of higher humidity, and >the sharpness is most pronounced in the low tenor. Vladan </blockquote></div> </div>