<html> The effect is also less noticeable on the notes directly above a rib, and most prominent at the mid point of the rib positions. The two sample pianos were a D and a SD10 in both cases it was < .2 cent pitch drop Test only done in Octave 6.  So no conclusions on my part. Roger At 06:51 AM 8/14/02 -0500, you wrote: <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite>I believe the right explanation should be approved by experiment.with out any experiment,here is my assumption for the phenomone:</blockquote> Baoli, I explored this some a year or so ago, and found an interesting correlation. Very often, taping off the rear duplex of the section eliminated the pitch drop when the second string was tuned in. <blockquote type=cite class=cite cite>if you shift to another partial(meaning you measure a different partial of the same note)the rare phomonene will probably disapear.Or if you lower the pitch a little bit the phomomee should disapera also.</blockquote> Not all that rare, from my experiments. The pitch rise happened about as often as unisons that didn't change pitch - at least in the piano I sampled in the shop. I didn't think to try measurement of different partials. Ron N </blockquote> </html>