[pianotech] Double Octave Stretch

John Formsma formsma at gmail.com
Wed Feb 10 20:44:32 MST 2010


Mark,

I had intended to reply to this earlier, but it got buried in other posts.
Sorry.

Though I wouldn't call myself a "concert hall tuner" because I don't do it
often enough, I do tune for our small symphony whenever they use the piano.
My preference is to have the piano in tune. 7 bps for a double octave is
wayyyyy too much, and is out of tune. The maximum that I can be comfortable
with is 2 bps in a treble double octave. Perhaps 3 bps, but I never
intentionally tune that much sharp. The other extreme is to have P12s beat
more than 1 bps. I think that's equally unsatisfactory, except that I prefer
stretched double octaves to shrunken P12s.

I think in most musical contexts more than that could sound OK to some and
not be too noticeable. Large pianos in halls will often experience pitch
changes (caused by temp changes) that can make double octaves to widen more
than 2 bps. There's often nothing one can do to prevent it -- and it ends up
being acceptable in the performance.

I regulate stretch by checking for perfect 12ths, particularly in the
treble. This gets the piano sounding best (to my ear). The double octave
will usually have 1+ bps, but never over 2 bps (after the unison is tuned).
I like the single octave tuned so the P12 below the top note is pure (after
the unison is tuned). There is some "activity" in the single octave, but not
excessive. More of a slight roll rather than a still octave.

When doing a "concert" tuning, I tune the unisons as I go. In my opinion,
this method gives the finest sounding tuning.

To sum up, get the piano in tune. Excessive stretch isn't helpful. My limit
is 2 bps for a double octave, but preferably less.

On Fri, Feb 5, 2010 at 3:05 PM, Mark & Janine Davis <
pianofortetechnology at saol.com> wrote:

>  Greetings List,
>
> I have read much about piano tuners preferred octave stretch.  I recently
> came across a grand piano in a fairly large school hall which had been tuned
> two weeks prior to me inspecting the piano on request.  The octaves were
> stretched 1 bps and the double octaves were beating almost 7bps.
>
> Rick Baldassin writes in his book “On Pitch”, pg 83.84,85…  ‘There are
> widely varying opinions as to where and how much to stretch octaves, and
> rather than impose my personal opinions, I choose to present facts and tests
> that will allow each reader to experiment and create his or her own opinions
> as to how and where stretching should be done… After all, in octave
> stretching, what we are dealing with is often more a matter of artistic
> preference in a grey area than random selection in black and white…Remember
> that when stretching the octaves, the demands of the double octaves must
> also be met.’
>
> My questions are, what are the demands of the double octave and what is the
> maximum stretch one can/does use in a big concert hall, once again
> considering the double octave demand?  In other words how much stretch is to
> much and the reasons why?
>
> Thank you, Mark Davis
>
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