Hi Greg. It is the soundboard that expands when humidity level goes up (any wood does). There is some crown in the soundboard shape, made to give a spring like counter force to the bearing force of the strings. When the soundboard expands, the crown in it lifts the bridge up, pulling the strigs sharp. Stéphane ----- Original Message ----- From: "Greg Casper" <gcasper@pacbell.net> To: <pianotech@ptg.org> Sent: Tuesday, March 12, 2002 7:27 AM Subject: They're going sharp, I tell you! > Just a general question from a relative newbie... What usually causes a > piano to sharp between tunings? Going flat is completely understandable, > from the string streching and/or pin loosening points of view, but what, > other than maybe temperature or frame flexing, can make a piano go sharp > over time? > > Thanks > > Greg Casper > >
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