[pianotech] PR follow up

[Israel Stein]

Fri, 28 Aug 2009 17:48:30 -0700 "David Love" 
<davidlovepianos at comcast.net> wrote:
>
> I don't see soundboard compression being a factor or that there is any 
> delay in response to added tension.  String segmentation tension 
> differentials I'll agree are a factor but those can be overcome with 
> proper technique and attention---I don't think they offer a reason 
> that the piano can't achieve stability. 
>
>  
>
> David Love
>
> www.davidlovepianos.com
>
>  
>
> *From:* pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] 
> *On Behalf Of *PAULREVENKOJONES at aol.com
> *Sent:* Friday, August 28, 2009 5:02 PM
> *To:* pianotech at ptg.org
> *Subject:* Re: [pianotech] PR follow up
>
>  
>
> The most general phrases that seems appropriate to start the 
> discussion would be soundboard (de- and re-)compression over both 
> bridges, and the string segmentation tension differentials. Seems 
> enough. :-)
>
>  
>
> Cheers,
>
>  
>
> P
>
David, Paul and all

I believe that the late Dr. Al Sanderson in his discussions of pitch 
raising contended that soundboard de- and re-compression happens 
instantaneously as the  pressure on the bridges changes  with the change 
in string tension, and there are no further changes over time.  So this 
seems to support David's opinion.

But there is another factor here that everyone seems to be ignoring - 
and that is the "memory" of the wire - the same factor that cause 
instability in a newly installed string. At least in a severe pitch 
raise or drop, what happens is that the section of the wire that was 
bent around a bearing point has now moved away from the bearing point 
and is expected to be straight. And a new section of the wire that has 
been straight is now bending around a bearing point. It will take some 
time for those segments of the wire to either become completely straight 
or to fully bend around the bearing point - just like a newly installed 
string. Perhaps less time than a new string - but nevertheless, some 
time. I am not going to speculate as to how long or how much of a pitch 
change would bring this into play. but this is the factor that - at 
least to my mind - suggests that a "follow up" tuning may be useful some 
weeks or months after a severe pitch change.

Israel Stein
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