[CAUT] How long to stabilize??

[reggaepass at aol.com]

Hi Fred,



Fascinating observations about unison behavior.  Do you also find patterns in how a unison will smear over time withOUT significant changes in relative humidity? (I know, if environmental conditions are stable, YOUR unisons probably stay in tune for ever.<G>  I'm just wondering why mine eventually go out the way they do.)




Thanks, 




Alan Eder


-----Original Message-----
From: Fred Sturm <fssturm at unm.edu>
To: caut at ptg.org
Sent: Thu, 19 Feb 2009 7:24 am
Subject: Re: [CAUT] How long to stabilize??







Hi Diane, 
  THere are a few patterns to pitch change due to humidity. The most noticed is at the tenor break, and also the treble break. But unisons go out in a pattern, also, on most pianos, usually more in the octave 5 and above range than elsewhere. This happens on Steinway Ds (I always notice after a rain, or sharp fast change in humidity, and call it unison smear - a cent or so overnight sometimes), but is especially noticeable in many Yamaha and Kawai models (not to single them out, also other Asian makes), where that treble section might stay closer to pitch as a whole, but with wide skewing of the left and right strings. Often one will be sharp of pitch while the other will be low, and the middle between. Also common is left or right on pitch, and the other below or above by quite a lot. Sometimes it is a 15 cent or more difference. Ouch! Nasty unisons mean unhappy customer. (Talking here about after a 20% or more RH change,
 over a period of weeks).

 I don't have an explanation, just observe it.

 

Regards,

Fred Sturm

University of New Mexico

fssturm at unm.edu





 



On Feb 18, 2009, at 8:47 PM, Diane Hofstetter wrote:


I haven't heard about the unison skew factor before--interesting, I will have to start measuring that.



=


 




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