The reason comes from the character of soundboard. Usually,the string try to move the board via bridge and play a absolutely dominant role for the vibration system(the string,the board,the case,etc').at the same time the board has a feedback to the strings.Tha's why we tuners tune the string-tension, instead of chiseling the soundboard(G). Because three strings have more power to shock the board(if one tune the union very well,so the strings would cooperate together) than a individule string,the pitch have the tendency to go flat if three string vibrate together in the same (or very close ) phrase.I tried to detune union and hope to see pitch raise(or less pitch drop).I am not very good at fine measurement,it seems the pitch will drop less after I detuned some unions by a few beats. Now let's think about why pitch could go sharp occasionally.like string,the board has his own "partials" which are called vibration modes.the modes of the board could have a strong feedback influence if the modal frequency of the board is very close to a string partial,this could cause a very noticeable "pitch drop", or "pitch raise" depends if the modal frequency of the board is a little higher or lower than the equivalent string partial. I believe the right explanation should be approved by experiment.with out any experiment,here is my assumption for the phenomone: one modal frenquency of the board is just below a string partial you are measuring,one string has the tendency to raise the soundboard modal frenquency because both have to vibrate together,but one string is weaker that two/three strings.so,if three string vibrate together,the string will force the board vibrate a little quicker than it's original modal frequency. 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. It's my assumeption only. Baoli --- Joseph Garrett <joegarrett@earthlink.net> wrote: > I have seen the phenomenon of two/three strings > being "flatter" then each, > individually. And, I accept Dr. Sanderson's > explanation of the reason for > the effect, more or less. However, I have also seen > a reverse phenomenon of > the unison being "sharper" then the individual > strings! Would someone like > to advance a theory on this???? > Best Regards, > Joe Garrett, RPT, (Oregon) > > I'm never lost, because everyone is telling me where > to go. <G> > __________________________________________________ Do You Yahoo!? HotJobs - Search Thousands of New Jobs http://www.hotjobs.com
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