Rick and Mike, I think my original statement may not have been clear, and its meaning may have been misconstrued. I was not, am not, saying whether the back duplex is good or bad, or whether it does anything or not. It does do something. What I said, and still say, is that an individual speaking length of a string does not couple across the bridge to it's corresponding tail the way it does to the string segment at the front duplex. It can't, unless the bridge termination is faulty. The strings of a unison will couple to their corresponding tails IF those tails are resonant with then. They will also couple to their neighbors above or below in the scale if they are resonant. For example: If the tails of a certain C are resonant with the overtones of the speaking lengths of the B below it, but not with their own, they will couple to the speaking lengths of the B, but not the C. The coupling takes place through vibrations of the bridge, and it will occur where there is resonance, whether that be the tails of the same strings or not. If you experiment with this, I think you will find that what I'm saying is true. I'm NOT talking about whether the undamped ringing of the tails is desirable or not. That's a matter of taste. That was never what I was talking about. I was addressing the myth in the minds of some people that energy goes across the bridge from speaking length to tail like it does at the front duplex. It does not, and cannot. Vibrations of speaking lengths will couple through vibrations of the bridge to any string tails in the general area that may be resonant with those speaking lengths. They don't have to be the tails corresponding directly to the speaking lengths. What you end up with is a plethora of undamped string tails. Yes, Mike, it is somewhat similar to the difference in the sound when notes are played while the sustain pedal is depressed, only not so much so. Sincerely, Jim Ellis
This PTG archive page provided courtesy of Moy Piano Service, LLC