Dear Don, While I salute your attempt to find a rule of thumb for RH: cents deviation. my gut feeling is that calibrating it on an instrument that drops as much as 108 cents when going from 45% RH to 18% RH may not be the "ideal case". I've got some 20 year old Wurlitzers that are that "flexible", and it drives their owners crazy (but they still don't get a DC system). Some models move (almost) that much, others are more stable. Perhaps someone with an inventory of Yamaha uprights, or Baldwin Hamiltons, can collaborate with you in your study. Patrick Draine
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