[CAUT] Tuning the back duplex

[Richard Brekne]

Hi Daniel

I wonder if you might share your reasoning as to why the tuning process 
will not allow for tension in the back length to remain higher then in 
the speaking length once the back length is set to a higher tension. It 
would seem to me that if one was careful not to move the speaking length 
tension overly much in tuning, that this would have no affect. Playing 
would tend to pull on the string... if anything tending towards more 
tension on the back length... tho perhaps if the tension on the back 
length was overly high  friction might slip and an evening out of the 
two segments might occur.

Another thing that strikes my thinking is what about the tension on the 
segment of string on the bridge surface itself.  Today I was working on 
a 7 year old D which has early stage killer octave problems developing.  
There was a good deal of phasing going on and some amount of bonified 
false beats (single string beating).  I virtually eliminated all of this 
by first pulling up the back length segment, then tuning with quite hard 
test blows with sustain pedal down to let loose any that I'd over 
pulled, followed by finding a pitch for the back lengths in which there 
was no false beat apparent for these lengths and tuning them as unisions 
to that pitch.  None of the resultant pitches for backlength unisons 
were consonant with the speaking lengths... so the problem you allude to 
with ringing after damping was not apparent.

I just got back from the concert where I heard the whole thing from the 
studio of the National Broadcasting company here in Norway at the 
concert hall in town.... not a hint of change through the whole concert. 
I'll see the piano again in the morning.  Interestingly enough tho... 
the experience did open my eyes a bit more into the world of the 
percussive problems of the killer octave.  Nothing like a high class 
studio to shed a kind of acoustic-microscope on piano sound.

Cheers

RicB



         > just what is the most optimal frequency relationship to the  
         > speaking length to tune these lengths too is another
        question.  I'm  
         > getting the feeling that if one assures that the tension is
        higher  
         > in the back length then the speaking length.... that you end up  
         > with a cleaner sounding instrument.... but I am still  
         > experimenting.  Any thoughts would be greatly appreciated
         >
         > Cheers
         > RicB

    I have not tread lightly here but delight in joining a fine mind in a  
    study in which many have indulged in passing as have I.
    I find as have you that higher tension is favorable, variable  
    tensions (read variable pitches) not commensurate with the series of  
    the speaking length are not too noticeable, but any piano with  
    tunable back lengths cannot stand perfectly tuned back lengths for  
    the resulting stridency of the ringing after damping.

    Again, my own experience indicates regular tuning process rarely can  
    keep the residual tension higher than the speaking length and that  
    higher tension on the back length could aid soundboard collapse.

    Your contributions are greatly appreciated and look forward to a  
    continuation of same.


    Daniel Gurnee  HSU Ret.


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