[CAUT] Tuning the rear duplex

[Richard Brekne]

Hi Andrew

I get the sense you are trying to set the tension on the back length 
outside of what its actual length allows for given the pitch you want 
for the speaking lengths.

IHMO there is quite a bit less actually known and shown to be true about 
what the back duplex length does and doesn't then there is opinion.  And 
much of the opinion out there strikes me as plagued with self 
contradiction.  So I suggest just keep experimenting on your own and 
keep asking yourself questions. 

A bit of experimenting  I've done shows more to my own satisfaction that 
the pitch of the back lengths relative to the speaking length most 
definitely can have an impact on the overall sound, and that the back 
length tension (if well within tension parameters for the string as a 
whole) remains quite stable when adjusted... more so seemingly then the 
speaking length... which strikes me as odd.  This said.. I've no hard 
data and complete objective study to back this up with, which puts my 
observations in the category of casual at this point.  Still, seems 
pretty clear to me that there is potential for adjusting the overall 
sound picture of the instrument here.

You can pretty easily find out what the back length with tolerate (with 
regards to stability) by making large changes in the speaking length 
tension.  Just check before and after status of the pitch in the back 
length to see when it changes.  Large changes in the speaking tension 
can have negative impacts (wear and tear) on the front termination 
tho... so I wouldn't advise making a general practice of that.

Cheers
RicB




    Continuing this thread...

    I checked a Steinway D at one school and the rear duplex was tuned to
    the speaking length fundamental for the last few notes.  At another
    school the rear duplex ranged from a minor 2nd to a major second for
    those same last few notes.  I tried tuning them and managed to pull
    the major second one down to a 1/4 tone sharp after tuning the
    speaking length.  It wouldn't stay down and I'm wondering about
    stability for the speaking length now.  I'm guessing this one is
    going to need some moving to tune a little closer.

    Observations?

    Andrew Anderson

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