John, Jim, Paul, Dave, Greg, Vince and all others following this topic, I revisited the Steinway upright today trying to identify the source of the resonation. I began rapping the board with my knuckle and then touched various areas trying to dampen any existing vibrations. While I can't say I pinpointed the problem exactly, I did rule out the strings. It was definitely not the strings or insufficient dampening. They were quiet. Also some of you had mentioned putting stringing braid in the non-speaking segments behind the bridge. This we had already done to my surprise (all 88 notes even). I did discover one unusual contributor to the problem. This Steinway had two wooden framed metal screens screwed onto the back side. They must have been there for cosmetic purposes as they shielded the backposts and soundboard. I rapped the soundboard with my knuckle after removing them and was able to get a two second reduction in the sustain time of the phantom sounds. With screens removed, the piano now has a sustain time of 5-10 seconds, after the knuckle rap on the soundboard, instead of 7-12 seconds. I remain committed to finding a way to reduce these sustaining sounds. Yes this board has the two features Jim Harvey pointed out, a "wave trap" at the top, (backside) and a solid hardwood lower right corner. It also has an extensive plate which runs out the bottom and back frame beams which are numerous, every 5-7 inches top to bottom. Tomorrow I'll go back with a helper to investigate again. I think I'll focus on the perimeter of the board and see if I can accomplish any dampening there. There's a two inch cavity where the rim is tapered down to the rim/board glue joint, on the treble side of the piano, where I may be able to stuff some wave absorbing cloth or foam. Thanks to all for the help, David Sanderson Littleton, MA Pianobiz@aol.com
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