<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"> <meta name=Generator content="Microsoft Word 10 (filtered)"> <style>  </style> </head> <body bgcolor=white lang=EN-US link=blue vlink=purple> <div class=Section1> The degree to which a string will change pitch with a given change in length (that’s what happens when the case, bridge, board expand or contract) will be a function of tension (or as Ron N has corrected me breakpoint %--though I have some questions about that).  The low tenor is generally the lowest tension (and BP%) and so changes the most.  Hockey stick type bridges are where you often see a huge drop off in tension at the bottom of the tenor bridge and it is on those pianos where the pitch changes are the greatest.  Pianos with more uniform tension through the bottom of the tenor bridge will not change in the same way.  The wound strings tend to be much higher tension (though not necessarily higher BP% and therein lies my question about which it is) and therefore change less.   At any rate, it has little to do with differences in the degree to which the soundboard crown changes in different parts of the piano.     An examination of the formula for frequency of a string as a function of tension (or BP%), diameter, length (BP%) and looking at the differences in the rate of change depending on tension levels should yield more clarity.      For example, take two strings of equal length producing equal frequency (the dependent variable) but with different diameters (gauges—they will have different amounts of tension and they will also have different BP%) and then change the length equal amounts and you should see a difference in the change in frequency between the two.  If someone has the formulas handy (too early for me to go looking) maybe they can post it.    <div> David Love davidlovepianos@comcast.net www.davidlovepianos.com </div> -----Original Message----- From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of David Nereson Sent: Tuesday, July 15, 2008 12:09 AM To: Pianotech List Subject: summer sharpness in low tenor   <div>     Most pianos go quite sharp in the summer because of higher humidity, and the sharpness is most pronounced in the low tenor.  But what I've seen quite often is that the lowest plain wire strings will be really sharp, but the wound strings right next to them on the same bridge won't be anywhere near as sharp.  How does this happen? </div> <div>     Also, one would think that the middle of the soundboard would experience the most swelling, which would in turn affect the mid-treble most, not the low tenor strings down there in the corner of the soundboard.  What gives? </div> <div>     --David Nereson, RPT </div> </div> </body> </html>