FW: Tuning Duplex

[Alan W Deverell]

This EXTRA post addresses some of the more fundamental issues very
well and I thought worthy of sending on to Piano-Tech - comments
welcome.

-----Original Message-----
From: Dr. Clive Woods [mailto:C.Woods@sheffield.ac.uk]
Sent: Wednesday, June 10, 1998 8:28 PM
To: Alan W Deverell
Subject: Tuning Duplex

At 13:11 on 10 Jun 98, Alan W Deverell wrote:
> My impression - tune to 1 octave above or 2 octaves or 3 octaves
above
> etc. so long as you can discern the pitch.

This is a real can of worms. My piano does not have duplex wedges but
when I've been able to experiment my impression has been that they
are tuned either to an harmonic of the fundamental (around the middle
of the piano) or to a note which has a harmonic in common with the
fundamental (at the top of the piano) (e.g. tuned a fifth above the
fundamental). Note that an harmonic here means any octave above, and
also octave and a fifth (3rd harmonic), 2 octaves + 3rd (5th
harmonic) and so on - i.e. the wind players' harmonic series.

> How much REAL benefit and HOW much cosmetic HYPE is there in this
> Duplex thing anyway?

That also is a real can of worms. I see definite benefit in having
the string the "other" side of the bridge undamped. This gives less
decay, more sustain. Presumably makers found that leaving the non-
struck lengths undamped introduced lots of undesirable resonance, so
they _tuned_ them. I don't think it affects the tone much, though.

> Most tuners in NZ never touch these wedges but Ron Overs made and
> fitted NEW wedges to some of his re-built Steinway D (unfortunately
he
> is not on e-mail to ask - so I immediately thought of you:-))

I don't think tuners touch them here either. I think (mind I say I
think) on some pianos they are fixed in the sense that there are
locating lugs on the wedges that fit into holes in the frame. On
others (e.g. Fazioli) they are definitely adjustable. I suspect no-
one except a Fazioli technician knows how to adjust these.

> If I remember correctly, these only sound a step or so above the
> speaking length pitch. Or maybe it was an octave and a step. The
> closer the bars are to the speaking length, the higher the pitch. Is
> this correct?
> Does anyone know how I could determine how these should be set?

If the settings are being doubted, I would refer to the manufacturers
for advice on that particular model. This I think is why some pianos
have fixed duplexes.

> In general, Kawai sets the aliquot bars so that they are tuned
> slightly sharp of some interval.
> Before everyone asks why Kawai sets them a little sharp, the answer
> is I don't know.

The answer to this is surely that the strings are inharmonic and so
they _have_ to be a bit sharp (not much) of the "mathematically
correct" note. For the same reason, the basic tuning is "stretched"
at the top.

> It's one of those questions I've never heard a
> definitive answer to.
> My question is about the rear duplex 'bars'.
> Is there a way to tell if they've been repositioned correctly?

Again, ask the manufacturer.

Clive
_______________________________________________________________

From: Dr. R.C. Woods, Department of Electronic and Electrical
Engineering, University of Sheffield, Mappin Street, Sheffield,
S1 3JD, United Kingdom.