why does a string go out of tune?

[Don]

Hi Wim,

Possibly you are pounding too hard. Very small changes in humidity cause
pitch instability in unisons. I've documented that on the ptg list. I wish
I had better tools to analyse what is going on. Temperature (stage lights)
as I'm sure you know can make huge differences very very rapidly.

At 02:22 PM 4/10/2004 EDT, you wrote:
>  OK, what exactly is happening when a string goes out of tune. I know
>about climatic changes that effect the soundboard. This causes the who
>piano, or at least whole sections to go out of tune. I can accept that. But
>I pride myself on setting the string and the pin. I am a pounder. On new
>pianos, (at least new to me), and especially concert instruments. I beat
>the daylights out the notes to get them to stabilize. But there are still
>strings that go out. That is why we tune concert instruments numerous
>times, with strings still going out.     lights standing absolutely still.
>But every time I tune it, the piano is "in tune" in that it hasn't changed
>pitch over all, but there are at least 2 dozen strings that have "slipped."
>They are 2 or 3 cents off. I'm not talking notes, I am talking string. The
>right string of one note is 3 cents low, or the left string of another note
>is 2 cents flat.    Why is that? Why do just these strings go out, and not
>the other ones? Am I still not pounding hard enough, or is the combination
>of slight variations in temperature, combined with strings that maybe
>weren't set right, causing this? Inquiring minds want to know.   Wim Willem
>Blees, RPT
>Piano Technician
>School of Music
>University of Alabama 

Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.P.T.

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