[CAUT] Humidity, Bridge caps, pitch drift

[Ed Sutton]

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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