Why a string goes out of tune.

Wimblees@aol.com Wimblees@aol.com
Tue, 13 Apr 2004 10:23:58 EDT


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In a message dated 4/12/04 9:21:15 PM Central Daylight Time, claviers@nxs.net 
writes:

Jim: First you say:

"This means that no matter how hard you pound, you will NOT equalize the 
tension between speaking lengths and string tails.  You will break something 
before you can pound hard enough to do that.  What you WILL do is cause it to move 
if it is about ready to move
anyway."

So I asked, if you don't pound, (or play softly), will the string move any 
way. So you answered:
No, Wim, I am NOT saying playing the note softly will equalize the tension
across the bridge.  You know that.  I said pounding will cause it to move
if it is about ready to move anyway.  If the tension is not equalized
across the bridge, but the string is about ready to move, but you play
softly, nothing will happen.  But if you do pound, or if the pianist
pounds, then it will move, and the pitch of the speaking length will change.
So does this mean I should pound to equalize the string? If I don't pound, 
and the string doesn't equalize across the bridge, then when the pianist plays h
ard and does move the string, then the piano will be out of tune. 


"Now consider the fact that you have a whole bunch of strings whose tensions
are only partially equalized across the bridge, because there is no way you
can completely equalize it.  All it takes is for the relative humidity to
change, the bridge to swell or shrink, or the temperature to change so that
the difference in expansion coefficient between wood and steel will cause
the string to slip a microscopic amount at the bridge, or someone to pound
the key; the string will move at the bridge, and your perfect unison tuning
will be spoiled.  I think this makes lots of sense."

To me you're saying two different things. On the one hand you're saying not 
to pound, because the string will move across the bridge anyway. But you're 
also saying the string won't move across the bridge until you (or the pianist) 
plays loud. So what is a piano tuner to do? Tune softly, and let the strings not 
move across the bridge, or play loud, and move those strings. 

The other thing you're saying is that a little change in temperature or 
humidity will cause a string to go out of tune. I can accept that to some degree. I 
saw your demonstration of that at one of the conventions. But you were taking 
a hair drier to a string on a mini back. On the concert stage, most of the 
time a piano is not going to be subjected to that kind of extreme changes. I 
would think that having the string equalized would prevent most microscopic 
differences. 

Now granted, pounding to equalize tension, and playing so you can hear the 
note, are two different things. I never said I listened to a pounding note as 
the final answer. All I said is that I pound to set the string and the pin. 

What makes sense to me is that if I don't pound every note, to get every 
string to equalize across the bridge, I'm asking for trouble. 

Wim 

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