Marshall, Remember when you are pitch correcting you are adding tension to the plate, measured in tens of pounds per string, maybe ton(s) per piano. Pianos are designed to have down-bearing. That is, each string presses down on that 1/4" thick but ribbed sound-board through the bridge. When you pull one string all the way back up to tension, guess what happens to its neighbors. They go flat as they have less tension to hold down. When you tune across a piano you are pushing a wave across the sound-board. Those of us with ETDs figure 10-16% over-pull in the wound strings, 20-28% over-pull in the tenor, 25-38% over-pull in the high treble. When we are done with the re-tensioning pass we check out how close everything settled. My estimates are getting better now and usually it all settles pretty close. When over-pulling aurally you will use the beats above correct pitch to guestimate your over-pull. Figure four cents per beat at A4, less lower and more higher. New pianos with new un-stretched strings are quite ungrateful, they'll loose your tuning faster than that old piano that you bring up to pitch. Unless, of-course, the pin-block was too loose to hold the tuning pins at tension. I've had a couple of those, definite CA glue candidates. Have fun, Andrew Anderson
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