[CAUT] Humidity, Bridge caps, pitch drift

[Albert Lord]

Ed,

Also, you may notice that the right strings of the unisons
(which terminate nearer the middle of the bridge) are
affected more by the humidity increase than the left strings
(which terminate nearer the front edge).  The right strings
of unisons will also lead the way down when the humidity
drops,  as will those unisons on the left of sections.  This
happens on uprights as well.

I'm sorry,  I don't know why.

Albert


On Fri, Jun 26, 2009 at 8:43 PM, Ed Sutton <ed440 at mindspring.com> wrote:

>  Here's the pattern I saw on a 5'2' grand piano:
>
> On the long bridge, in each section, the leftward bridge notches terminate
> the speaking length in the middle of the bridge. As the scale ascends, the
> notches progress toward the front of the bridge. Crossing the gap at the
> plate strut, the notches start again at the middle of the bridge, and step
> forward again to the front edge. At the next strut, the same thing happens.
>
> The piano was humidity struck. At the leftward end of each section, where
> the strings terminate at the center of the bridge, pitch was 10-15 cents
> sharp. As the scale progressed toward the front of the bridge, the
> pitch drift became less, and was almost at pitch as the notches came close
> to the front edge.
>
> This pattern was repeated in each section.
>
> Why?
>
> Ed S
>
>
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