Hi to all: Raising the pitch of a string 1/2 step adds 12 to 15 pounds tension. Multiply this by over 200 strings and you get around 1500 additional pounds. Many factories tune a piano 1/2 step high on the first chip tunings. The plates are usually over designed to handle the extra loads. I did however see a grand which had a broken plate because our monsoon weather raised it about 40% of a 1/2 step above regular pitch. This was a Gulbransen small grand with a high tension scale to start with. Normally I wouldn't worry about the rescaling breaking the plate. I've never seen it happen due to rescaling. Just be sure that the plate is not warped out of its natural shape. It can stand lots of tension, but not much bending. Jim Coleman, Sr.
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