<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> <title></title> </head> <body bgcolor="#ffffff" text="#000000"> Hi Terry Grin.... good question.  And as you are no doubt aware at this point there is a lot of speculatation about the answer but no real definitiv answers.  Hard to isolate the effect of the mass of these aggraffes from the vertical vibrational modes bit.  I did put the question directly to Wayne Stuart about a year ago, who btw seemed like a very nice fellow, and he replied simply that the concept was well researched and documented mathematically by CSIRO Mathematician Dr Bob Anderssen  who did the research and that anyone who wanted to could contact him if they wanted more infomation.  To quote: <blockquote>Dr Anderssen has found out how the new coupling method is responsible for the wonderful clarity of sound that the Stuart pianos produce. By exploiting existing knowledge about piano sounds and string vibration, some of it over two thousand years old, Dr Anderssen was able to build a mathematical model of the way piano strings vibrate. "The model reveals how, in standard grand pianos, the strings begin vibrating vertically but change to vibrate horizontally, parallel to the soundboard," Dr Anderssen says. "This change to a horizontal vibration makes the sound less harmonious." "But, in the Stuart piano, the vibrations stay in the vertical plane because of the special coupling method implemented by Stuart. This gives a more harmonious and stronger sound," he said. </blockquote> Strikes me that if folks want answers to these questions then  Andersen is a good place to start... followed up by a good deal controlled testing.  Speculation... armchair or otherwise may be fun and perhaps even thought provoking... but it remains speculation. Cheers RicB Terry Farrell writes: How would sideways tension (I think more like intermittent point-source longitudinal compression) on the bridge reduce the ability for the soundboard to vibrate more freely? Whatever tension or compression or whatever forces are within the bridge - not the soundboard. How would what is/isn't going on in the bridge affect soundboard performance? Terry Farrell </body> </html>