Duplex

[Ron Nossaman]

>However, our experience has been that the rear duplexes exhibit quite 
>good tuning stability. 

Meaning what? That they don't go out of tune with humidity swings, or don't
go out of tune farther than the longer speaking lengths do, as they
logically should? 


>One added benefit we have found with tuning 
>the rear is that the tuning stability overall seems to be slightly 
>improved. I don't attribute this to any 'magical' qualities. But I do 
>suspect that the process of actually tuning the duplexes also causes 
>the back scale tension to remain closer to that of the speaking 
>lengths. 

Ok, are you speaking here of the initial positioning of the aliquots, or
the measurement and adjustment of duplex pitches during the course of
regular tuning? We have different factions using the term interchangeably.
They are entirely different concerns, and I'm trying to separate them here.


>Over time, for pianos in which only the speaking lengths are 
>tuned, the back scale tension falls as the sound board gradually 
>takes on compression set and the 'crown' recedes slightly. 

How can this possibly be? Haven't we already determined that strings will
render across bridges? Didn't you just indicate that you are sure
longitudinal vibrations make it from the speaking length, past the bridge
pins and across the bridge to the duplex? How can they do that if the
string refuses to move on the bridge to the point that the back scale
tension falls as the soundboard crown deteriorates? How much time are we
talking about here?   



>After some 
>time, when the big hitting pianist comes to town, the tuning 
>stability goes horribly wrong as the speaking lengths are pounded, 
>pulling the tension of the back scale up and killing the tuning. 

I've found this likely to happen in the Winter months, when the piano is
pulled up to pitch for the tuning, leaving the back scale somewhat low in
tension. I've also seen individual strings go sharp after play in the
Summer months, when the pitch is lowered during the tuning, leaving the
back scale somewhat higher in tension. This is exactly the point I'm trying
to make about the duplex segment not maintaining the same tension as the
speaking length, regardless of their length ratios. 


Ron N