>Doesn't humidity typically cause an increase in crown, as the wood cells >swell across the grain (like grains of rice getting fatter, not >longer)? If so, this would cause the center of the soundboard to deflect >more than the edges, affecting strings on the parts of the bridges near >the center more than the high treble -- or what? > >--Cy Shuster-- Hi Cy, Good observation. This, among other things, is why the assumption that soundboard rise and fall is the primary reason strings go out of tune with humidity swings doesn't make sense. The amount the soundboard would have to rise and fall, and the deflection angle changes that would result just don't happen to the degree necessary to produce the pitch changes we observe. More than soundboard crown changes, bridge cap swelling pushing the strings up the pins, which are slanted, making the string take a longer path across the bridge, stretching it more, and raising the tension and pitch. The string path in each unison will increase about the same because the pin angles are usually the same throughout the scale, but the overall string length in the treble is less, making the percentage of length change greater, making the tension change greater, making the pitch change greater. That's what I think is happening. Ron N
This PTG archive page provided courtesy of Moy Piano Service, LLC