My response is posted to everyone not just those people here I picked to hit the reply button on. I am reading so many responses that are saying "I do not know the causes of why the piano goes out of tune and then I read BUT, that word but seems to come into play a lot. But, I do not THINK it is the sounding board etc... If you do not know and if you do not think you know, how can it quantify an answer that seems to be more of a guess than an answer to the question? If I am reading it in this manner then others must be as well. As we all know, places like Michigan have severe weather fluctuations all year long. There is no real constant level of humidity here. Pianos are changing tuning here all of the time. Again, as most of us know, pianos do not lose the humidity that they acquired and retained from the summer months over night. It takes time. Nor, does the piano suck in moisture over night as the humidity begins to increase again. The wood of the entire piano will be absorbing humidity for the whole time the humidity levels are higher than the humidity content of the wood itself and it will be very slowly letting this same humidity out again, until the humidity levels begin to increase during the next seasonal change. It is during these time periods that the piano is ever so slowly changing tuning and changing pitch. I believe the entire piano is subject to these changes as about 75% (give or take) of the piano is made out of wood. I also believe and was taught that the sounding board which is the largest and only area of the piano to come into contact with the bridges and therefore, the strings, is the main culprit for these severe changes of tuning and pitch. The sound board and then consequently, the bridges and then of course, the strings, are expanding and contracting continually with the constant weather and humidity changes. It makes these changes most in the center of the piano which is why that part of the piano always sounds the worst. The bass section of the piano changes the least. Why? Because the bass bridge is located the furthest away from the center of the sound board on the piano. The same reasoning applies to the highest notes of the treble section. The treble bridge is located way over to the right, away from the center of the piano where it changes less. So, I believe then, because of these changes, that the middle of the piano is forcing the increase in tension and pitch making the piano go 1/4 + tone sharp during the summer months and 1/4 + tone flat during our winter months. A - 1/2 tone difference. Now on the other hand, if we keep the climate the same, the tuning and pitch changes very little. Therefore, I submit to you, what else could it be other than humidity changes and the sounding board flexing, forcing these expansions and contractions onto the bridges and therefore, onto the strings themselves. another factor for consideration. During this expansion, it forces strings upward onto the bridge pins which is why they must at some point, be gently tapped back down again. I do not believe this little bit of difference of the strings being up on the bridges make that much of a difference in pitch but, they do make a large difference in tonal quality and false strings but, that is a different matter. While there are other factors involved too such as heat, the harp expanding, strings expanding from heat and other things, those are not the focus of my attention at this time. What are your thoughts on this? Jer -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman Sent: Saturday, April 03, 2010 12:38 AM To: pianotech at ptg.org Subject: Re: [pianotech] Pitch Change (was: Grey market pianos, seasoned pianos, etc.) Thomas Cole wrote: > Trying to understand how a lossy termination results in a lower pitch, I > imagine that there is an effective elongation of the speaking length due > to the reduced rigidity of the drier wood parts in the cap and root of > the bridge, and possibly the board, and that there is an effective > shortening of the speaking length when those parts are made more rigid > by the uptake of moisture. In other words, a less stiff termination is > more likely to move with the vibration of the string and so the actual > point of termination has to be somewhere behind the bridge pin. Effectively, yea, that's it. It's been observed and noted (if not quantified to infinity) in actual trials. A flexible termination acts like a longer speaking length than a rigid termination. In a piano, this would translate into a string of given tension on the high humidity (higher compression/stiffer) board producing a higher pitch than the same string at the *same tension* on a dryer (lower compression/more flexible) board. It makes it a lot harder to come up with a simple consumer grade one sentence specific explanation of why pianos go out of tune with humidity changes, but I'm becoming more convinced that it's a real factor. Ron N -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100403/917672cf/attachment-0001.htm>
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