Topic by Jake Johnson

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Topic: The effect of having differing string lengths within unisons?

I'm still trying to wrap my head around Bechstein's intentional use of differing string lengths in a unison, so that the two or three strings each have a different inharmonicity. I'm not finding much information about the subject.

This exchange on the Piano World Forum says that besides Bechsteins, older Baldwins and at least one Steinway D have a similar arrangement: http://forum.pianoworld.com/ubbthreads....655/3.html . Oleg says in that exhange that one effect is to allow tuning wider octaves. To increase the stretch, in other words. On the other hand, David Pinnegar gets lovely results using Bechsteins tuned to precise or slightly raised octaves--tuning to the fundamental, if I understand correctly, or to 2:1.

But my thoughts start going in circles when I try to imagine the effect on coupling, the decay, the phasing of each partial, and the effect that a slight, realistic variation in attack time on the strings would make when a hammer isn't entirely true or grooves form at unequal rates. And each change in tension will move some partials in the pair or trio in and out of tune, so to speak, with each other. Seems to be something that could offer enormous possibilities in shaping the sound, along with enormous headaches in trying to predict and control the results with a tuning hammer.

(But at least we're one step closer to modeling an older Baldwin, now. We know one of its features!)

Last edited by Jake Johnson (04-02-2019 00:10)

Reply by David Pinnegar

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Re: The effect of having differing string lengths within unisons?

That sounds interesting.

It might also be to get what are thought to be richer harmonics.

Nowadays I'm tuning without stretch in the central three octaves. This is critical to Kellner and to Kirnberger III where C#2 to F4 can be really horrible if stretched further than the temperament. Then I'm tuning bass below tenor C so that the octave and or fifth based harmonics from the bass strings fall upon the temperament scale notes in the middle or tenor octave, and all unisons as exact, laser-like as I can make them. This works on the 1885 Bechstein but also on all modern instruments I've tuned.

I haven't observed different length strings in the unisons for any of the Bechsteins I've tuned, from the mid 1880s to a 1895 model through to one of the 1930s.

In the maturing of observations and ideas I'm starting to regard standard tuning as putting a layer of glass or ice over the music, the music shining through despite the instrument, the tuning having the purpose of dazzling the listener into worshipping the wonderful brand of the instrument. In contrast the families of temperaments with numbers of perfect fifths are harmonically arranged and provide key colour of musical chromatism and aural landmarks and anchors.

Best wishes

David P

Reply by Jake Johnson

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Re: The effect of having differing string lengths within unisons?

David Pinnegar wrote:

That sounds interesting.

It might also be to get what are thought to be richer harmonics...


...I haven't observed different length strings in the unisons for any of the Bechsteins I've tuned, from the mid 1880s to a 1895 model through to one of the 1930s...

Best wishes

David P

We may be talking about different things. For greater accuracy, I should have written that Bechstein gives the strings within unisons different speaking lengths. The actual length of the overall string isn't the concern. Or are you saying that the speaking lengths are the same on the Bechsteins you've worked on? I don't have access to any Bechsteins, so I can't check.) I'm going by the Piano World thread and the Bechstein-sponsored film I referenced in the first post in this thread:

https://www.forum-pianoteq.com/viewtopic.php?id=6306

Well, here's the direct link to the film:

https://www.youtube.com/watch?v=vgecQ1uytSA

The technician speaks of the different speaking lengths at around 8:12. He mentions them again a little later, saying that they create an "extra dimension." Bechstein seems to be saying that it is a unique and significant contribution to their sound. (Bechstein seems to have produced this video, so I'm assuming that the technician restoring the piano speaks for the company. Perhaps not.)

The difference in speaking length is not large--1/4" to 1/2". Not sure how much it would affect the inharmonicity. And I would imagine that the change in length would affect different strings--different brands and different thicknesses along the scale--to varying degrees.

Last edited by Jake Johnson (04-02-2019 17:36)

Reply by David Pinnegar

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Re: The effect of having differing string lengths within unisons?

How absolutely fascinating. I haven't see this on any of the Bechsteins I've tuned. Presumably for the state of the art largest and concert instruments only . . .

But it makes sense. The friend technician from whom I've learned much over the past years talks of a string giving false beats as "Bechsteining" and so internal beating of the note was assigned to the brand, and the term appropriated by technicians to a false note rather than clearly the intentional harmonic singing. Of course the now commonplace harmonic bridges are often detuned (horribly) so have taken the function of the multi-length strings.

Very fascinating.

Best wishes

David P

Reply by Jake Johnson

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Re: The effect of having differing string lengths within unisons?

(Looking at the film again, I see that the difference in speaking length appears to be very small, judging from the angle of the bridge pins seen at 8:55. Maybe 1/8 of an inch at most between each pin? But more of a difference between the length of the two outside strings on trichords, of course. Earlier, I was mistakenly looking at the end pins attached to the harp, even though the tech is clearly pointing at the slight slope of the bridge pins.

The slight difference makes me wonder still more about how much difference the extra length makes in terms of inharmonicity. Must have some effect, or Bechstein wouldn't keep it, and wouldn't spotlight it in this video.)

Last edited by Jake Johnson (07-02-2019 04:46)

Reply by Lizbetha

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Re: The effect of having differing string lengths within unisons?

I think the differing speaking lengths may be a phenomenon of the older pianos. My husband (also a piano technician) reminded me that Steinway C's (the 7'4" model, no longer produced) had different speaking lengths also. He describes it as a headache for the tuner, but perhaps we could reframe that as "an opportunity." And the technician in this film talks about the changes in production criteria, and losing something of value because of it.

Reply by jcfelice88keys

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Re: The effect of having differing string lengths within unisons?

Jake Johnson wrote:

The slight difference makes me wonder still more about how much a difference the extra length makes in inharmonicity. Must have some effect, or Bechstein wouldn't keep it, and wouldn't spotlight it in this video.)

Hello Jake,

You would be surprised and amused by the things various piano manufacturers do to differentiate their own brands from the rest of the market!  Take Steinway's "accelerated action" for instance:  In Steinway pianos, they round off the fulcrum of the key actions on which the actual wooden key notes rest.  Since the point of contact does not stay exactly constant as the wooden note rotates over the fulcrum (because the fulcrum is NOT a knife edge), that ever-so-slight difference has caused Theodore Steinweg (-way) to market his "Accelerated Action"! 


Also the notion of duplex scaling (in my opinion) is a cure without a disease, in the way that Yamaha International markets duplex scaling!  They claim that the overtones of the smaller length of string between the hitchpin and the agraffes on the bridge can NOT be tuned in harmony with the speaking length of the string!  I have plucked those short distances in the so-called duplex scaling ... and the notes are tuned all over the place, with regard to the speaking lengths of the strings, especially when one approaches the uppermost octave of even their finest concert grand pianos!!!

This is my opinion only, and I speak from 50+ years of tuning pianos of all sizes, brands, and qualities.  Surely other opinions exist in the piano world, especially by internet "experts".

Cheers,

Joe

Reply by David Pinnegar

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Re: The effect of having differing string lengths within unisons?

A friend of mine who helps me with research on instruments and tuning wrote to Bechstein about this

This was the response:

I recall Peter’s grand that he also introduced to Pierre-Laurent Aimard, who played it in a concert in Wigmore hall. To my knowledge, this specific arrangement of bridge pins was not used for all models and all periods, only for certain models in a certain era that unfortunately I cannot specify. I also assume that this was done for the sake of a more lively tone. We believe that softer brass bridge pins contributed to the phenomenon that you describe, unisons of vintage Bechsteins seeming more “lively” than those of other brands.

Best wishes

David P

Last edited by David Pinnegar (06-02-2019 23:38)

Reply by Jake Johnson

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Re: The effect of having differing string lengths within unisons?

I experimented with the string length parameter in Pianoteq and found that quite a large change in string length was required to make a change of one hz in the lower partials. And that upper partials (above the 8th partial, usually) changed more readily as a string's length was changed.

At first, this made me think that slight variations in string length might have little effect the pitch of partials, and thus on the sound of a unison,but two things come to mind:

1. Those upper partials do contribute to the perceived pitch and "brightness", and will beat against other partials on the other, longer or shorter, unison strings, creating a perceivable effect.
2. Very small changes in pitch can make a large difference, as we know from working with varying temperaments. Changing a pitch 2 or 3 cents can lead to a very different sound when chords, particularly, are played, so couldn't similar small changes within a unison change the sound of the "chord" created in the unison string?

Last edited by Jake Johnson (09-02-2019 21:04)