Tuning Duplex

[Ron Nossaman]

According to the patent specification Clark just posted, and the drawings
with accompanying text Dan published in the Journal article, the principal
player in the duplex saga is the tuned front duplex. The tuned rear duplex
isn't indicated at all in the Journal drawings, but is in a footnote as a
means for the tuner to have "perfect control of the proper adjustment of
tone and transport of the tension over the bridge", and is mentioned in the
patent specification as a means of avoiding unharmonic tones from
longitudinal vibrations across the bridge by converting these vibrations
into harmonic tones. The description of the action and supposed benefits of
the front duplex was pretty detailed and well thought out, whereas the rear
tuned duplex seems to have been thrown in as an afterthought. Perhaps the
idea was to include it in the patent while they were at it so someone else
wouldn't later, but it is clearly not the primary concern of the patent. So
we've been hearing for some time about this marvelous patent resulting from
a collaboration between the all time geniuses of acoustic and piano
research and design that seems to me to be dealing almost entirely with
something other than the tuned rear duplex. The wording of the patent,
furthermore, indicates to me that the rear duplex was intended as much as a
testable audible indication of segment tension, for the benefit of the
tuner, as for tone enhancement and noise reduction. This also indicates to
me that it was quite well understood at the time that no amount of
repositioning the rear duplex aliquots will itself result in a tuned rear
duplex, but that the segment tensions will have to be equalized by string
manipulation with each tuning, assuming the aliquot is finally accurately
positioned in the first place and left alone thereafter. Since it is more
than a little likely that the aliquot positioning isn't accurate from the
factory, given the wide variations in speaking lengths from piano to piano
of the same model, accurate repositioning of the aliquot will most likely
be necessary, if it is possible, to allow tuning of the duplex, but does
not in itself constitute tuning the duplex. After the permanent final
optimal position of the aliquot is established, rear duplex tuning will
have to be done by direct string (not hammer) manipulation, not moving the
aliquot, each and every time the piano is tuned to meet the requirement of
having been even remotely perfectly controlled by the tuner to provide
proper adjustment of tone and transport of tension over the bridge. 

In talking about this stuff, we need to do a few things that have been
largely  overlooked or ignored altogether. We need to clearly differentiate
between the front and rear duplexes, since each is an entirely different
beastie from the other, and they are not remotely functionally equivalent,
much less interchangeable. We need to differentiate between just moving
aliquots,  just manipulating segment tensions with the aliquot in unknown
position, or manipulating segment tensions with the aliquot in previously
verified accurate position. If we can't do that, then none of us will ever
know what the other is talking about, much like we're doing now, and if we
live to be a thousand, none of this will ever be cleared up. Not that it
ever will be anyway, but we should at least make an attempt at intelligent
communication.
 
Ron N