Stretch: What's it all about?

[Richard Brekne]

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You've run smack into one of the issues piano tuners just love to
debate... sometimes rather hotly. Myself I tend to aggree with Randy
more then I dont in this case.

In the end tho... because you are trying to come up with the "best"
match of a set of coincident partials that allow you only one pure pair
at a time, the whole thing is necessarilly a bit subjective in nature...
withing limits.... wishfully reasonable ones :)

The differing  OT's in Cyber ear can be used to assure a reasonable
stretch or misused to impose a stretch that artifically further
stretches or compresses the pianos natural inharmonicities as Randy
would see them.  Any ETD can be used to do either. And aural tuners do
the same thing regularly.

I always suggest new tuners who are at all interested in finding out
about piano inharmonicities to download a copy of Tunelab 97 and start
matching partials "manually" to build different kinds of stretchs into a
tuning. Then by comparing the phase display notes with coinicidents at
the frequency being looked at one can very methodically familiarize
oneself with how all the various octave types, fifth, and twelth types
progress throughout a tuning. When you know enough about how it all fits
together.... you can make up your own mind about the "stretch" question.

My View

RicB

"Nelson. Gene (PWA)" wrote:

>      I am kind of a newbie, so if this topic is a dead horse
>      that's already been beaten a few times, forgive
>      me.
>      What I would like to do is briefly describe my understanding
>      of stretch and ask for comments about
>      whether I am getting the idea or not.
>      Randy Potter states the following: "We are simply trying to
>      match our tuning to the amount of
>      inharmonicity in the piano". (Randy Potter course book,
>      section 1.6). "You do not put any stretch in
>      the piano. The piano told you how much to stretch it. ...
>      using 17ths and 3: and 4: octave tests, you
>      would end up with a perfectly stretched piano". (section
>      1.7)  What he is saying is, minimize
>      octave beating, and then a piano is stretched correctly.
>      Well, recently I bought the Reyburn Cyber Tuner, which has a
>      "Octave Tuning Style" feature, which
>      gives the user a range of 9 levels of stretch you can choose
>      from; "1" being "pure" (beat speed for
>      the 4:2 octave at A2-A4 = 0), and "9" (beat speed =
>      0.8/sec.) I was immediately confused because
>      this contradicts Potter, who says a piano is tuned "right"
>      when octave beating is minimized, period.
>      Meanwhile, I can remember a physics professor explaining
>      that human hearing is "imperfect"
>      because when we hear a pure octave, we think it's a little
>      bit narrow, so pianos are stretched in
>      order to make octaves sound more correct to the human ear.
>      No one has ever explained all this to me succinctly. What I
>      have concluded in my own little
>      pea-brain is that there are two distinct kinds of stretch:
>      what I will call "objective" and "subjective".
>      The objective stretch is that which compensates for a
>      piano's inharmonicity.
>      The subjective stretch is the amount beyond the objective
>      part, which makes it sound good to the
>      listener. So when people use the word "stretch", they're not
>      always talking about the same thing;
>      sometimes they mean the objective part of it, sometimes they
>      mean the subjective part of it,
>      sometimes they mean both parts, and sometimes they don't
>      know what they're talking about.
>      Right ??
>      Any guidance on this subject is welcome.
>
>
>
>
>
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--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html


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