deep in the unison, (was Bluthner something)

[A440A@aol.com]

Mark writes:

<<  With all  due respect, I think the analogy to a swing is not quite 
perfectly 

applicable, 

         Agreed, it is not perfectly applicable.  At least, not perfect in 
the sense of a mathematical model.  

>>     If the swing's period is 5.0 seconds, and you always apply your push 
.1 

seconds after the swing has changed directions, so that you are adding 

force in the same direction the swing is now travelling (this is what I 

think you meant), then the period of your push is also 5.0 seconds, not 

5.1 as you suggested. Your push is slightly, but consistently, late, or 

out of phase, and therefore is simply adding amplitude, as to a pendulum.<< 
 
>>    If instead you actually did time your pushes to 5.1 seconds, with each 

successive cycle you would get .1 seconds further behind the 5.0 second 

phase of the swing, until you were actually colliding with the swing 

coming at you from the opposite direction. Where at first you had been 

adding amplitude, this would gradually change until you were acting 

against and cancelling out the opposing force. 


     There is a distinct difference in a pendulum that is free and one that 
is driven. ( I am too far removed from the physics courses to exactly explain 
the differences).  What I remember is that the pushed pendulum steadily 
increases its speed AND amplitude, so the 'collision' would be farther down the line 
than the simple timing of the two factors would indicate.  Even so,  the 
collision would only happen once, and then the cycle would begin anew. As soon as 
the swing crossed the line and met the push, it would be reset to its original 
timing and the push would once again be in phase.  
     Not sure what the hell that has to do with Bluthners, but coupled string 
behaviour is not so well understood that we shouldn't continue to kick the 
possibilities around.  Sooner or later, somebody with an engineering or physics 
background will stroll out onto this playground and paint the lines for us.  
    It may be my own imagination, (rogue scoundrel that it has shown itself 
to be), but when I tune two strings of a unison as exact as possible, and then 
tune the remaining string slightly sharp,  it seems that the sound has less 
power and sustain than when the third string is slightly flat.  I am talking 
about the least amount necessary to cause the SAT to indicate direction.  There 
is no beating, but I swear I hear a different sound. 
Could others please try this and let  us know if the effect is real or 
imagined to them?  
 
>> I think we can agree that when one string is slightly out 

of tune with another, the rate of the beat that results exactly equals 

the difference in their frequencies, and this brings me to my main 

point: I have never been able to detect any kind of locking, coupling, 

or accomodation of one string to another, and believe me, I've tried, tuning.

and I wish I could.  <<

        I have found that all three strings can be so close together that the 
unison sounds dead, and I don't hear that 'aftersound'.  Move one of them the 
smallest amount possible and the unison seems to fill out and last longer.  
Is this caused by there being a beat that is twice as long as the audible 
sustain, so we only hear half of it before there is a collision between the push 
and the swing?  I dunno.  I know that organ pipes draw frequencies together if 
the pipes are close enough to be air coupled.  Sails on sailboats certainly 
affect one another by the coupling of their laminar frequencies.  (angry people 
can make those around them angry, etc).  
I am not ready to say that one string's behaviour doesn't have any effect on 
its neighbor.  


>> And here's one point: it is in 

manipulating the rise time of this beat that we are able to create the 

illusion that the decay time of the note has been increased.<< 

<snip>  We can no more make the note last longer than the 

input energy through the string-bridge-board-air makes possible, than we 

can make water flow uphill.>>

        I can't quite go that far.  I think that what we hear is a result of 
the efficiency of the system, and the frequencies must certainly have 
something to do with that.  I also don't know how to tell the difference between the 
illusion of increased decay time and what is actually there.  Seems like if it 
sounds like it is sustaining longer, it is.  
    Anyone else wandered around in this thicket?? 
Regards, 
 
Ed Foote