Duplex

[Ron Overs]

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Dave and Duplex-Dan,

Dan wrote:

>. . . The duplex can be way out of tune and many pianists as well as 
>audience may
>not mind.

Similar to some concert tunings and CD recordings. And sure, a number 
of pianists are just 'key pushers' and similarly with regard to 
audiences, many will be cloth-eared. But there will always be a 
couple who can hear.

>Your note does include an interesting idea that has been used successfully by
>tuners who tune duplex scales.
>The idea of "massaging" the duplex scale.

Yes Dave well said. But it has been mentioned on this list before. 
Maybe you weren't paying attention DD.

>Basically what this is is stretching, as when putting new strings on a
>stringed instrument. This does bring the string down and provide a stretch
>and evenness to the string .

I don't agree - I've gone through this all before on the list - twice at least.
What if the duplex tension was low and the block too close to the 
bridge also, causing the duplex pitch to be sharp even though the 
duplex tension is low? Will rubbing the duplex segment to tune it by 
lowering its pitch 'provide a stretch and evenness' as you put it? No 
- by rubbing the duplex length in this situation to tune it, the 
duplex tension would be rubbed down to be even lower in tension, 
relative to that of the speaking length. If the situation as 
described (at paragraph start) were to occur, assuming that the 
duplex and speaking length were in fact tuned at the previous tuning 
by rubbing and not moving the block, the speaking length would creep 
flat as the duplex went sharp (since the duplex tension would be 
lower). This creep would gradually occur since the changing dimension 
of the hygroscopic bridge cap, which causes the strings to rise and 
fall while in contact with the bridge pin (as Ron N so beautifully 
described in his Reno bridge class), would encourage the string to 
creep across the bridge cap slowly in an effort to equalise the 
tension on either side of the bridge (you see Ron N, while you were 
discussing vertical bridge movement in your class and its 
predisposition to falseness, I was thinking off topic about its 
relevance to the way in which string creep occurs when the string 
segments aren't at uniform tension - I had previously understood the 
reason, but not the facilitating agent for string creep at the bridge 
- and no, DD, creep will not occur around the hitch pin since the 
steel hitch pin is not hygroscopic). This would cause the duplex to 
go sharp and the speaking length flat. This would tell us that the 
block is too close to the bridge. Is that all as clear as mud in a 
beer bottle now? You see, if you were to rub the duplex to lower the 
pitch without moving the block, the unequal tension would in this 
case be made more unequal. Hence the tuning stability would be worse 
not better. On the other hand, since we determined that the block was 
too close the bridge, when we move the block away from the bridge, 
the duplex pitch drops maybe going through pitch to flat, then we rub 
the speaking length to bring the duplex up into tune. What happens if 
we move the block too far away from the bridge when we adjust it. 
Well when we rub the speaking length we will have to rub too hard to 
get the duplex up, causing the duplex tension to be too high even 
though it is in tune. During the inter-tuning period, the reverse 
will occur, the duplex will go flat while the speaking length goes 
sharp. What do we do then at the next tuning (when we find out that 
we stuffed up last time), we move the block back in closer to the 
bridge, by what we hope is about half of the original adjustment. And 
on it goes - incremental refinement is the name of the game.

>But as to the application of this stretching to
>a tuning job, I can not recommend it if it is used in lieu of placement of
>the harmonic bridge.

Yes and no! Massaging the string cannot be used in lieu of moving the 
block, or vice versa. The two procedures must be used together as 
described in the previous paragraph, with an understanding of what's 
actually happening regarding the string tension on both sides of the 
bridge. But it should ideally be done at the time of a subsequent 
tuning. In my experience, it is necessary to return to a previously 
tuned piano (and I mean tuned with a proper hammer technique - not a 
tuning where the 'tuner' is swinging the pitch all over the place 
like a flag in a breeze), in order to fully understand where the 
string segment tensions and the block positions are at. It is when 
the piano is subsequently retuned after a solid and accurate tuning 
that we get to understand which blocks are positioned correctly and 
which they are not - by reading the string creep across the bridge. 
When the bridge creep ceases, and it will eventually if the designer 
and builder have done their bit properly, you know you've finally 
arrived. That is, provided that the piano scale was designed in such 
a manner that the percentage of breaking strain is uniform from note 
to note - provided that the information was transferred accurately 
from the CAD drawing to the real world piano, then the piano just 
might stay in tune - provided that hammer technique . . . . . . 
.provided that the pin block is  . . .provided that. . . Isn't this 
fun !!

>The duplex portion of the string is comparatively short and the most
>effective method of tuning this segment, and having it stay in tune is to
>adjust the placement of the harmonic bridge (duplex) to a point on the plate
>that promotes a fundamental duplex tone that is in harmony with the speaking
>length.

 From my experience, yes and no. Sure we want to achieve an in tune 
duplex segment, but moving the blocks alone won't get you there with 
stability. You cannot achieve tuned duplex stability by moving the 
blocks alone without also massaging the wire (on whatever side of the 
bridge is determined to be appropriate). It would not be possible to 
just move the blocks around to achieve a tuning of the duplexes, 
without also taking stock of what's also happening with regard to 
duplex tension. One cannot just use a simplistic approach to this 
stuff. Paolo Fazioli was the first person to bring tuning of the 
duplexes to my attention back in 1994, when I spent days at the 
factory with Hiener Sanwald discussing this and many other matters. I 
believe that it takes experience doing it combined with a modicum of 
thinking it through, when working with duplex tuning to understand 
what is happening. If we are going to discuss this stuff, then let's 
think through what is actually happening DD. It was only a couple of 
weeks ago when you were calling  the front-detuning fraternity the 
naysayers, not a particularly helpful turn of phrase perhaps. Well I 
can tell you DD that some of those 'naysayers' have thought about 
this stuff for years as I'm sure you have too, and some of them have 
even gone to the trouble of building pianos of their own, after 
rebuilding everyone elses stuff for about fifteen years for a 
backgrounding - while modifying the manufacturers products all the 
while to prove or disprove a point. (Steinway Hamburg seem to have 
heard of our little 'workshop of ill repute', judging from some of 
the grapevine comment that has returned over the years, and their 
threats of legal action for modifying their precious designs. Once in 
1996 I was accused of using non-Steinway agraffes in a D, but they 
were Steinway New York agraffes instead of Steinway Hamburg - I had 
tried to get Hamburg agraffes but the relationship had gotten so 
frosty with Hamburg that the local dealer wouldn't supply. I never 
did get to tell them what really happened, but then again would they 
have listened? - talk about the left hand not knowing about the right 
hand) Anyhow, so called enquiry can come occasionally with its 
unwanted pressures, even if we are only involved in the tiny piano 
industry - I digress. Furthermore DD, some of those 'naysayers' have 
deliberately sought out folks who disagree them along the way so that 
they might, together, slog it out to reach some sort of truth - 
though occasionally only a truce. Several months ago John Hartman and 
I had a disagreement on this list, in which it became obvious that we 
both had very different yet strongly held views about bridge capping. 
Now, after further reading some of John's Journal articles on other 
topics, I have come to understand that he is a very knowledgeable 
technician. Sure there are differences in approach between us which 
are still very much I suspect as they were, but I would very much 
like to have a frank and friendly discussion with John at some future 
time - it would be interesting I'm sure. We don't have to all agree, 
but at least we should all think about why we think the way we do. 
Let's at least think about the parameters we are dealing with here 
before taking off irretrievably on our particular tangents. You never 
know, sometimes we think we're saying something different, when 
closer attention can reveal that occasionally, two different folks 
can be saying the same thing from opposite sides of the fence (or the 
ditch), without realising that there are more similarities than 
differences. I'll shut up now - keyboard's due for an oil change.

Hey Terry, how's that jpeg coming along? Yes Ron N. soon I'll compose 
a draft on the pare.

Ron O.






-- 
Overs Pianos
Sydney Australia
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Web site: http://www.overspianos.com.au
Email:     mailto:ron@overspianos.com.au
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