"pounding"

[Ron Nossaman]

There's something else here that I've noticed that hasn't been addressed.
When doing a quarter semitone or more pitch raise on some pianos, an odd
thing happens in the high tenor and treble on the second pass. After a
string is tuned adequately, often a sharp rap will knock it down about
three or four beats. It will only do this once. Further pounding has no
positive effect, and a quick check will indicate that the other two strings
have settled too. The immediate response of pitch change from tuning hammer
movement prior to the sharp blow indicates that it is NOT coming from
unequal segment tensions forward of the bridge, so it is definitely NOT a
hammer technique problem. That only leaves two possibilities that I can
see. The first is that the coils spontaneously settle around the pin and
the pitch drops accordingly. I guess this is a possibility, since it's easy
enough to demonstrate how drastic the pitch drop can be by tapping directly
on the coils, but I can't see the shock of a hard blow going past at least
two bearing points and arriving at the tuning pin with enough power to
settle the coils. That would seem to leave possibility number two, which
looks to me to be considerably more likely. That is that the strings render
through the bridge, more nearly equalizing tension between the speaking
segment and back scale. That would also explain why this is much more
noticeable with a big pitch change, than with a minor one. I assume it
happens more in the high tenor and treble for two reasons. The total string
length from the rear bridge pin back to the hitch is greater in proportion
to the length from the front bridge pin to the tuning pin in this area than
it is further down the scale. That means there is proportionately greater
elongation potential in the back scale, so more string can render across
the bridge to "equalize" (though it's highly unlikely to be exactly equal)
tension in the segments. Also, a little string movement makes a bigger
difference in pitch in the top half of the scale than in the bottom half.

In defense of this idea, note that when doing a pitch lowering of over a
quarter semitone, pitch often tends to drift slightly high in these same
areas as you tune the second pass. That would be the higher tensions in the
back scale slowly pulling the string sharp as it renders across the bridge.
Pounding does no good whatsoever when doing pitch lowering. Didn't you ever
wonder why, when it is often the only way to get a pitch raise to stay put?
When pitch lowering, I find that hitting them fairly gently, but in rapid
succession, and a lot of blows, will settle them better than anything else
I've found. If you keep them moving, they slide better.

All this also indicates to me that one can't state with any certainty that
hammer technique alone will take care of this problem. I would say that at
least one fairly "firm" blow per unison, at pitch, is absolutely necessary
when pulling a piano up to pitch. Dropping pitch, or tuning something that
is already at pitch is a different story.


I know that I'm the only guy on the planet that thinks strings render
across bridges, but I don't account for my observations any other way.



Ron N