post pitch-raise creep?

[John M. Formsma]

David,

 

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. My goal is for most of
the piano to be reasonably close to pitch rather than A4 be exactly at A440.

 

I use a 33% overpull on most pianos at A4 - after getting the best average
of how flat the treble and middle sections are. After pitch raising, the
middle section will usually be very close to pitch, and A4 will be slightly
flat. That means A4 has dropped during the pitch raise to below the original
target. I think this drop is because things shift around as you're pitch
raising, and A4 changes as you set the temperament octave and move up toward
A4 and beyond. Sometimes A4 will end up 5 cents flat - sometimes less. But
most of the time, everything else in the middle is very close. So I don't
worry so much about A4 and focus on the bigger picture of the rest of the
piano.

 

Now, another way I suppose you could do it is to use your 41% overpull for
A4 only, then make A3-A4 beat 1.5 bps or so, which would mean a lower A3
around the 33% mark. (That should make things even out in the end, although
I normally don't do this -- just speculation.)

 

Another thing is that the tenor doesn't need as much overpull as the A4
region. So I consciously pitch raise those octaves a bit flat so they won't
be sharp during fine tuning. This is particularly noticeable on spinets and
consoles, and I have enough experience with other pianos to guess pretty
well.

 

One thing that has really helped me do aural pitch raises is TO NOT WORRY SO
MUCH ABOUT IT!!!  I'm "shouting" at myself too because I need the constant
reminder not to pick nits until the piano is close enough in tune to tune
it. ;-)

 

This is one area where the ETD users might have an edge on us aural people.
However, the piano will still change for them just like it does for us. And,
when your machine screws up for some unknown reason and calculates the pitch
so that it ends up 4 cents sharp, then it has made more work rather than
less. (This happened twice when I was using the Verituner. I thought my
AccuFork was off b/c of a low battery, but it ended up that the Verituner
had some screw-up that day that made it add 6 cents to what the overpull
should have been. So I was fighting a sharp piano during the fine tuning -
yuck! and trying to match it to another piano in the same room - double
yuck!) Seems like the best policy is to schedule a real fine tuning after a
few days when the piano has had time to settle down and behave. But, alas,
most of my customers don't normally do this.

 

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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