A 440 Standard (PS)

[James Ellis]

In a post I sent earlier, I mentioned that I measured a -0.56 cent change
in pitch per degree F change in temperature.  In looking back through my
data, I see where it measured -0.92 cents per degree F at another time.  It
boils down to what I said before.  It's a matter of rate of change, and how
much error resulted from change in plate temperature and thermometer lag.

I just read Don's post again, and I take exception to one statement he
made.  He said that he had found that changes in "harp" (plate) temperature
had virtually no effect on the pitches of the strings.  Oh, but it does
indeed!!  I think he means, "provided the strings are at the same
temperature as the plate".  If that's what he means, then he's right.
Otherwise, he's wrong.  The cast iron plate and the steel strings have
similar, although not identical, coefficients of expansion.  The point is,
it is very difficult in the real world to change the temperature of the
plate without changing the temperature of the strings too, and the strings
will change much faster because of their low mass, as opposed to the
massive plate, which will change temperature very slowly.

Now:  On the practical side:  Many times I have been tuning a piano in a
cold church, and someone will come in and offer to turn on the heat for me.
 I will tell them "NO, thank you.  Please leave it just as it is.  I don't
want the temperature changing while I'm tuning the piano".  Come Sunday,
when everything has been all warmed up for several hours, including the
pipe organ, the piano will be fine, and so will the organ, and they will be
together, provided I tuned the piano to A=440 at whatever temperature, and
the organ technician tuned the organ to A=440 at the temperarture where it
will be played.  Otherwise, the two will be a world apart.  If there is a
sudden temperature change during the service, the organ and the piano will
go in opposite directions, pitch wise.

It is amazing at how close the piano will come back to the same pitch at a
different temperature, provided the temperature is stable during the tuning
process, while it is being used, and all parts of the piano are at the same
temperature in each case.  The ideal situation is to tune the piano at the
temperature it will be used, but sometimes that isn't practical.  The big
"NO NO" is for the temperature to be changing while the tuning is going on.
 That will get you a bad tuning every time, especially if you are using an
ETD.

Jim Ellis