The affect of temperature and humidity on stability of pitch of various areas of the S&S B and D. 2/17/09 Before I retired from HSU I performed some measurements on performance pianos when tuning stability showed a fault. I feel rather in line with Richard Brekne. Tuning the day of a program was not always a guarantee of unisons and the tenor break. Touchup was a regular need just before the program. On that general occasion, lights were a problem and with the hall filling(200+ persons) produced a change in humidity and temperature. The temperature effect came immediately and the humidity effect came on during the performance, usually in time for touchup during the intermission. When the lights came on before the performance, the heat increased the temparature of the metals, the wire being the most suseptable, increased in dimention to relax and go flat. The shortest ones going flatter because their length gave up a higher percentage of their tension. The longer ones gave up less and the middle ones gave up less than the short and more than the long but all were flat from the affect of the lights. As long as the lights remained on the effect remained. If the piano was moved, I now had a new consideration. Humidity wise, it has been generally understood that humidity will affect wood by three days. My measurements of pin movement by block expansion/contraction indicated mid performance with the effect of audience moisture that the right pin of a unison moved farther from the capo/agraff than the left pin. The measurement taken by michrometer was assumed to be pin block expansion which may have been caused by humidity or temperature. During performance this effect was indiscriminate because though it was happening it was too small for a determination. However over a long period of larger humidity change, the longer string going further sharp being farther across the block from the plate ridge than the short string being on a shorter width of the block; with the humidity increase the long string went sharp to the middle and the short string went flat to the middle string, all strings going sharp by their own percentages. I disregarded the bridge to plate segment because for small changes in apitch that segment rarely if ever changes with a change in tension. By the way, Greg Granoff as my replacement at HSU is very much the technician and musician. Daniel Gurnee, HSU Retired -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut_ptg.org/attachments/20090220/b8fe3aa3/attachment.html>
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