Stretch: What's it all about?

[Nelson. Gene (PWA)]

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My question would be: within the octave/s that you are experimenting with
have you tuned all of the other notes? If so do the thirds, fourths, fifths,
sixths fit nicely? If not then your stretch would need to be modified. The
introduction of contiguous major thirds was a wonderful method of
demonstrating just how much an octave would need to be stretched. If you are
working on a spinet or a small poorly scaled piano there will be little
chance of sorting this all out. 
Another idea here is: If you try to tune an octave as you progress up from
the mid range and you tune to "minimize octave beating" as suggested, you
may find that you have made the 2:1 partial quiet as this tends to have the
most volume in this part of the piano. Then you will soon discover that your
octave is too narrow.
Gene Nelson
 
 
 -----Original Message-----
From: D. B. Stang [mailto:stangdb@voyager.net]
Sent: Tuesday, February 25, 2003 08:39
To: pianotech
Subject: Stretch: What's it all about?



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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