The theory that pitch drops when several strings of a unison sound together because of lowering impedance at the bridge makes sense to me, but let's follow that theory to its logical conclusion. When the note is first struck, all three strings are in phase. They are going up at the same time and going down at the same time. While they are doing this, their combined efforts make the bridge appear to be easier to move because they are all pushing and pulling together. That makes the termination point on the bridge appear to be a little beyond the physical termination point, so the pitch becomes lower. But the relative tuning of the three strings may not be perfect. Some time before the sustain dies out, it is quite likely that one string will get a little ahead of or behind another. They will no longer the pushing and pulling together. In fact, there may be times when two strings are acting in direct opposition. At such times the bridge will appear to be stiffer than normal and the pitch should actually rise above what it was for a single string. Whether this effect can actually be observed depends of how long the note sustains. But if two strings differ in tuning by 1/4 beat per second (at the partial being measured) then there should be a pitch drop for the first two seconds and then a pitch rise for the next two seconds. -Robert Scott Ypsilanti, Michigan
This PTG archive page provided courtesy of Moy Piano Service, LLC