Actually there is very little temperature variation in our music building. Occasional temporary glitches in individual rooms, but overall, remarkable stability. Humidity, on the other hand, can easily vary by 20% from one day to the next, and gradually shifts during each day. This is due to requirements for HVAC (heating, ventilation and air conditioning) that require complete air exchanges in public buildings every hour or so (I forget what the interval is, but it may be more than once an hour). At any rate, my comments about unison drift in response to humidity change are not based on any individual piano, but rather on observation of many, many pianos over 15 years. I pay most attention to my observations in the music department, as I have more knowledge of intervening conditions there, and see the instruments more often. I also have large numbers of individual models, and am able to observe patterns that apply to a Baldwin Hamilton as opposed to a Yamaha U-1, for example. But I see the same evidence in private homes to a lesser degree, and certainly in churches, private schools, and other locales. Sometimes the variations are relatively minor (more in the one to two cent range), and by no means is there a complete consistency throughout the entire range of all instruments, but there is definitely a consistency to finding the right string (treble side) drifting farther than the left, if they don't sometimes even go in opposite directions. And, as I wrote earlier, this can happen to such an extreme degree that the difference is in excess of 20 cents. The extreme case seems to be mostly in octave seven, but sometimes in octaves five and six. At some point, I hope to have the time to do more than mere off the cuff observation, and chart pitch over an extended period of time on a few instruments. I started to do that a while back, but I kept noticing other things I wanted to keep an eye on, so I would need to add more strings to read (initially, I was just looking at the variation across breaks and the like). I'd sure be interested to know if anyone else has made observations that come anywhere near tracking mine. Regards, Fred S. Sturm, RPT University of New Mexico Mark Bolsius wrote: > > Fred, > You make some interesting observations... > > I wonder if the temperature variations that brought about the humidity > change may have something to do with it? > > If the pianos that do this are the same ones and other don't, then > monitoring of temperature as wel as humidity would be necessary, but > possibly the environments with these "troublesome" pianos may have some > thermal anomaly happening in them. Remember that temperature change also > causes humidity to change... > > Just a thought > > Cheers > Mark Bolsius > Bolsius Piano Services > Canberra Australia > > ----------
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