[CAUT] String Coupling / SB and Bridge stiffness...and maybe Pure Sound

[Ed Sutton]

Ric-

Unfortunately I had to glue in some keybushings, and my mind took over...

In thinking about strings and soundboards, etc., we proceed by conceptually 
isolating the various components, when in reality they are always 
interconnected. Consider the role of the non-playing strings when you try to 
measure the pitch of one string in a tri-chord unison. They do not magically 
evaporate, changing nothing. Played or not, they effect the system.

>From the viewpoint of the sounding string, the non-sounding strings are 
increasing the impedance of the bridge/soundboard/string system that the 
single sounding string is trying to move.

A. If the two non-sounding strings are muted, they are in effect coupled 
with their half-step neighbors, and presumably their impedance does not 
change over time.

B. If they are not muted, but are left open when one of the tri-chords is 
plucked, they would first add to the impedance, then perhaps, as they began 
to move in response to the bridge motion, they might work either with or 
against the original string, depending on the phase shift.

C. If all three strings are struck, is there an amplitude threshold for 
coupling to take place via the bridge? Is it the same as the amplitude 
threshold for the system to produce audible sound? If not, what will we hear 
when two or three coupled strings de-couple? Can we hear them de-couple at 
one partial, but stay coupled at other partials? If this can be heard, it 
might be your diagnostic for system impedance. Perhaps this is the hissing 
sound of a killer octave with poor sustain.


Meanwhile, I had an interesting talk with Virgil Smith this evening. He is 
doing well and has been writing some new material about how tuning can 
change the sound of a piano.

Ed S.








----- Original Message ----- 
From: "Richard Brekne" <ricb at pianostemmer.no>
To: <caut at ptg.org>
Sent: Thursday, June 11, 2009 3:33 PM
Subject: Re: [CAUT] String Coupling / SB and Bridge stiffness...and maybe 
Pure Sound


> Hi Ed
>
> I think by and large we agree here, tho I am less certain that we are on 
> the same page on a couple points. Comments interspersed below.
>
>
>    "The Tune-Offs" have become legendary. I was not there, but reports
>    from people who were there convince me that nothing was proved. No
>    recordings or measurements were made. In fact, the legends are
>    seriously misleading about what happened. Jim Coleman may have kept
>    his tuning offsets, and about half the audience felt his tuning was
>    better than Virgil's. I don't think Jim considered the events to be
>    serious studies.
>
> I tend to agree for the most part, tho I might add that if they did show 
> anything conclusively, it was that the audience(s) of these tune-offs were 
> not capable of discerning much of a difference from their listening 
> positions...which may say more about the audience(s) then anything else. 
> I would also point out that Jims tunings were not strictly by the dial, by 
> his own admission. It would be more accurate I think to describe his 
> tunings as ETD assisted tunings.
>
>
>    I do not know what the limits of Olympian human pitch perception
>    are, so I don't know that human hearing is more accurate than
>    digital measurement. If we were not somewhat tolerant, no one would
>    have pianos, because we all know they deviate significantly within a
>    few days (if not hours) of tuning, and yet, we still enjoy them.
>
> I think we first need to precisely define what the term <<accurate>> here 
> is before we get into comparisons between aural and etd based tunings. 
> For my part, accuracy can either mean "to what degree the result 
> corresponds with the intent" or it can mean a more vague attempt at a 
> subjective assessment of clarity and cleanness of overall in tuneness.  It 
> is this second we get into real difficulty with in such comparisons...yet 
> in the end it is usually this that lies at the root of our own personal 
> likes and dislikes. Now if someone can make that monumental leap and 
> bridge the gap between a purely objective math model to the degree that it 
> unifies in a nearly universal way all our individual sense of in-tuneness 
> ... that indeed would be a mark in human history. Such a gap has never 
> been bridged.  Heck physicists cant even agree on what gravity is or isnt, 
> or what causes it to come into existance.
>
>
>    I also don't know what is the correct or perfect tuning, and I have
>    seen people, including myself, have their opinions moved more by the
>    natural smokes and mirrors of the situation than by genuine response
>    to the rarities of temperament and tuning. (Sometimes I've been
>    moved by my own smoke and mirrors, and have a video to prove it!)
>
> I refer to the definitions above and otherwise echo your experiences. Its 
> hard to get at...yet somehow we always react positively when an instrument 
> really displays that in-tuneness that somewhere somehow apparently does 
> exist.
>
>    I hope I am an open minded non-believer, looking forward to learning
>    something, but I am empiricist by bent of character. Although I can
>    see how an infinite number of angels can dance on the head of a
>    tuning pin, I gently dust them off to make room for my tuning lever.
>
> :)... I'm not much one for smoke and magic either... tho like you I catch 
> myself at it often enough.  I'm just trying to apply simple logic here.
>
>
>    Therefore, I look for very simple numbers. I would like simple
>    measurements in controlled and fair comparisons. I would like to
>    hear, measure and compare "Pure Octaves," for instance. If the
>    measurement of Mr. X's and Mr. Y's octaves are the same, on the same
>    piano, and yet they ascribe to different methodologies, that tells
>    us something. If Mr. B's "pure octave" is a different measure than
>    Mr. C's "pure octave," that also tells us something.
>
>    Ed S.
>
>
> Agreed that measurements and numbers can be enlightening... but they cant 
> truly describe the world... or any of its constituent parts... and this 
> includes tuning.  It can only come close. Thats perhaps because numbers 
> reflect an ideal yet the world does not and can not conform to any ideal 
> in anything close to an absolute sense.
>
> Cheers
> RicB