Tuning Duplex

[John Delacour]

At 10:12 AM -0600 11/15/01, David M. Porritt wrote:
>Dan:
>
>I was thinking of your post while tuning a Steinway this morning.  If
>Ted Steinway thought so much of the duplex idea (actually tonally as
>opposed to as a marketing ploy) why did he make the duplex device not
>individually tunable.  When you cast the duplex oliquot as he did you
>assume a precision of plate casting, bridge placement and notching
>(both front and back) that just doesn't happen.  If you can really
>get the first and last notes of an oliquot plate "in tune" the rest
>of the notes are at the mercy of the above mentioned precision that
>just doesn't happen in these one-of-a-kind, hand-made pianos.

There's nothing "one-of-a-kind" about string plates and provided the 
pattern is accurate then the horizontal relations between points will 
be identical in every casting.  The only variation possible is in the 
thickness of the casting owing to variations in the closing of the 
boxes and quality control would reject any castings beyond certain 
tolerances.

As to long bridge placement and notching, what variation have you 
actually detected and recorded, as opposed to merely presuming?

Even if there should be minute discrepancies in the fixed 
relationship between the front partials and the speaking length, 
these can be compensated for in a minute difference in tension 
applied to them, which, owing to friction, will not travel past the 
bearings any more than the huge errors left by most tuners in the 
tension of the partials.

I did ask Dan to publish the original patent so that some semblance 
of objectivity and science could be brought to this wandering and 
opinionated thread and a few comparative oscillographs would speak 
far more convincingly than anything I've read so far.  I notice that 
as soon as I brought a few numbers into the "all in a row" thread, 
the silence was deafening!

JD