I've been too busy to get to this until today. The problem of unisons going out in response to humidity change is one that has puzzled me for years. It is definitely there as a consistent problem. I note it to be particularly extreme in the Yamaha G-2's under my care, but also to varying degrees in just about all other pianos, including Steinway model B and D. There is a consistent difference between left and right strings, sometimes as much as 20 cents in mid to upper treble (Yamaha. Steinway as much as 10 cents) after a change of 40 to 60 percent (over the summer, with next to no use or tuning). Talk about wild unisons! I, too, initially thought it must be me, some fault in my technique, but years of observation have convinced me otherwise. For example, a Steinway D, over night, in response to a rise of 20 percent ambiant humidity (a rain storm during a dry period) had almost all unisons, tenor through mid treble, consistently out of tune about one cent average. The right string had gone sharp, left flat, middle generally right on. My general observation is that the right, or treble, string almost always drifts farther than the middle or left strings, in whatever direction the piano has moved. I thought the general wisdom about this being a result of relative lengths of "waste lengths" (capo or agraffe to tuning pin) explained this, until I noted there was little or no such effect between adjacent unisons on a Steinway B (with the offset unison pattern in the plate/block: greater difference in waste length between adjacent unisons than between strings within any unison). I have no explanation, but simply want to confirm that this is a commonly observed phenomenon (or at least it happens here in New Mexico). My best guess is that it has something to do with bridge roll combined with notching, more for lack of any other explanation than because it actually seems plausible. Wild disparities at various breaks - tenor, mid-treble - are also common. On the G-2's mentioned, often the tenor break will be 40 cents sharp, this will decrease to about 20 cents to the treble break, then the first note above that break will again be in the 40 cent range. And the high treble is often flat. All this in response to the summertime rise of 40 to 60 percent. Have to get back to raising all that pitch I spent so much effort lowering a couple months ago. But it's the unisons that are driving everyone nuts more than the pitch. (I decided it wasn't my tuning technique to blame when I realized that my unisons would hold beautifully for months when the humidity remained stable. One rain storm, or the beginning of the evaporative cooling season, and all harmony disappears). Regards, Fred Sturm, RPT University of New Mexico Mark Bolsius wrote: > > G'day Geoffrey, > > Sorry I'm alittle slow getting back on this, and I may be prepeating what > someone else has said...but I get the CAUT list as a digest... > > As far as I'm aware, this phenomenon is common where the piano has had a > temperature shock of some sort. While the pitch patterns over the whole > piano indicate the typical humidity fluctuation, the unison variations are > absolutely typical of thermal shock. > > It could be a result of a teacher or student using a fan heater in the room > or any other one of a thousand possibilities... > is it under an air-con duct? > look into the use patterns of the room and if possible monitor the habits of > those in the room on a regular basis...if you manage that, I'm sure the > whole list would like to know how you did it! > > Mark Bolsius > Bolsius Piano Services > Canberra Australia > > ---------- > >From: owner-caut-digest@ptg.org (caut-digest) > >To: caut-digest@ptg.org > >Subject: caut-digest V1997 #172 > >Date: Fri, 29 Oct 1999 1:01 AM > > > > > But the tenor unisons were atrocious. When I checked the pitch of strings > > individually, the shortest string, ie. attached to the tuning pin nearest > > the capo, was generally a little flat; the string on the middle pin was > > either at pitch or a little flat; and the string on the pin closest to the > > keys was very flat. A really large difference in the way the strings or > > pins behave between the front and back of a unison. Same pattern throughout > > the tenor section and to a much lesser extent in the middle section.
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