post pitch-raise creep?

[John M. Formsma]

Sorry to post again, but the first paragraph in my first post wasn't as
clear as it should have been. It should read as follows:

 

Sounds to me like you're pitch raising aurally, which is what I'm doing.
>From what you're describing, I'd say that you are setting the wrong goal of
getting A4 to be exactly at A440 after a pitch raise. It sounds like you're
setting A4 too high, which makes the middle section sharp.  My goal is for
most of the piano to be reasonably close to pitch rather than A4 be exactly
at A440.

 

<snip>

 

John Formsma

 

 

  _____  

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Nereson
Sent: Friday, July 07, 2006 2:24 AM
To: List Pianotech
Subject: post pitch-raise creep?

 

    I do many many many pitch raises -- almost every piano I tune, for the
last 27 years.  (Almost everybody lets them go too long.)

    I've found that the ideal average overpull is halfway between 1/3 to 1/2
the amount sharp as it was flat.  In other words, a 41% overpull of the
amount it was flat.  For an easy-figuring example, say the piano is 18 cents
flat.  Half of that is 9 cents and a third of that is 6 cents.  Half-way
between 6 and 9 is 7.5, so I pull it 7.5 cents sharp, and almost invariably
A4 ends up right on 440 Hz, or very close.  

    However, if the piano is a half-step flat, I don't pull it 41 cents
sharp.  That would be too much.  There's some degree of flatness where the
usually-ideal 41% overpull has to taper off.  For a half-step pitch raise, I
usually overpull so that A4 is beating about 5 beats sharp.  That's
approximately 20 cents, I believe.  Sometimes more is required, sometimes
less.  It varies.  That's here in Denver -- probably different elsewhere.  

    But what I often experience is:  even though after the pitch raise, A4
is at 440; after I've gone through the fine tuning and      pulled in
unisons, when I go back to do the final check and touch up anything that has
slipped, I find that the whole middle section is sharp!  Why?

    --David Nereson, RPT

 

 

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