[CAUT] coupled motion and other myths

[Richard Brekne]

Hi Ric

The coupled motion of strings is a description of the physics behind how 
more then one string effect both the termination and each other when put 
into vibration.

The so called pitch drop Virgil Smith, Dr Coleman and a host of others 
claim is a related subject matter but it is not in itself the same 
thing. More like a predictable result when two strings combine to force 
a bridge into vibration.

It is in my opinion entirely possible that in some instances the pitch 
will not drop, but raise... or not seem to be affected.  The reason for 
this is also to be found in the 5 lectures.  The bridge impedance at 
each bridge pin also must be considered.

Another interesting and highly respected modern piano researcher, Dr. 
Nicholas Giordano from Purdue is worth reading on this and related 
subject.  He has for example recently shown conclusively that the 
longitudinal vibration mode of the string is quite a significant... for 
not to say decisive part of the attack portion of the sound the 
soundboard releases, and that this effects the overall sound.  He also 
has some interesting things to say about longitudinal vibration in the 
soundboard itself.

There are many piano techs claiming to have far greater insights into 
these subject matters then they can possibly have.  The fact is there 
are a handful of bonified researchers out there with the physics 
knowledge to describe adequatly these things, and all of these that I 
have read or talked to are quite ready to remain quite humble when 
claiming anything like <<conclusive truths>>  If it can be measured, 
fotographed, or otherwise observed... then ok... but complete 
descriptions as to why most of these things happen are still mostly very 
advanced ponderings.   Very well founded perhaps... knocking on the door 
of understanding perhaps... but ponderings none the less. 

Cheers
RicB



    Is this pitch drop that Virgil Smith mentions, is it the same as
    "coupled
    motion"?  Did he call it that?  Who then came up with the name?
        
    I can demonstrate the opposite.  I can tune a unison that will show the
    pitch rising from the first string tuned.  And this would be a
    unison that
    agrees with any RPT.   Lets do it at a convention.  I will pay for
    the booth
    if each visitor chips in a dollar.  (As an added truth, I can also
    demonstrate it can go down in an acceptable unison.)  That ought to
    make it
    worth $2.00 a visit.    Richard Moody    

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