[CAUT] IRe: Unison drift (was Reading low humidity/seasonal SB failure)

[Greg Newell]

Hey Fred,
         Thanks for the reply. I'm concerned that 
you may have taken me in a way that I had not 
intended. I'm sure that you provide wonderful and 
stable tunings to whomever you may be serving. I 
just thought I toss out the idea. I should have 
known that you would have tried different tuning 
schemes to narrow down your search in an answer 
to this puzzle. Next time I will try and be a 
little more thoughtful in my response.

best,
greg


At 07:36 PM 3/8/2006, you wrote:
>Hi Greg,
>     When I first noticed this, I suspected tuning technique, sequence,
>whatever. I experimented in many ways. Initially I tuned completely aurally,
>completely strip muted. I pulled unisons in different ways, sometimes all
>right strings from the top (pulling the mute one at a time), then left
>strings from the bottom. And other permutations, particularly when I
>switched to SAT about ten years ago (and was able to quantify it). I have
>tuned left string first, right string first, middle string first. Doesn't
>matter. I have convinced myself over the years that I can actually do a
>solid tuning, but that severe RH change will affect my unisons.
>     Now the extreme case I mentioned, on Yamaha G-2s, happens in the late
>summer, after a rise of a good 40%, with the average pitch of the piano at
>+25 - 40 cents. Far more common are more subtle changes. But it was the G-2s
>that really got me thinking about it, making notes to myself, documenting.
>     I now use RCT, and it is very convenient for observing this phenomenon.
>In pitch raise mode, simply read left and right strings alternately, unison
>by unison, as you tune upward (or whatever direction). Then go back and read
>those numbers, and see if you have a saw tooth pattern for the most part.
>Sometimes it's subtle, just a cent or two on average, other times it is
>quite striking.
>     Again, I don't claim to have reliable answers to why, but I do have a
>pretty good wealth of years of observation. I'll throw out another couple
>things I have observed, having to do with pitch change in response to RH
>along the treble bridge:
>1) On most pianos, the typical pattern has a large change at the bottom of
>the treble bridge, lowest plain wires, which decreases up to the treble
>break, then just above the break there is a big leap of pitch change.
>Strangely, Hamiltons do something different. Same large change at the bottom
>of the bridge, tapering to about midway towards the break, but then pitch
>change increases again approaching the break. Above the break, pitch change
>is suddenly less.
>2) High treble varies a lot from model to model. On Hamiltons and some
>Steinways (especially 1098s) the top couple octaves tend to be the furthest
>off pitch, maybe 40 cents sharp where the tenor was 25 cents. Yamahas tend
>to have more movement elsewhere (tenor, just above treble break), but the
>high treble is closer to pitch than other areas.
>     I suppose there must be reasons, but I haven't found them. But I know
>what to expect, and it makes my life seem a little more rational, less
>random, I guess.
>
>Regards,
>Fred Sturm
>University of New Mexico
>
>
>On 3/7/06 8:29 PM, "Greg Newell" <gnewell at ameritech.net> wrote:
>
> > Fred,
> >        First I'd like to thank both you and Ron
> > Nossaman for your patience in explaining why you
> > fret as much over the humidity changes as you do.
> > It does seem that you can make rather astute
> > predictions in the resultant outcome of a
> > seemingly minute climactic change. Admirable!
> >        I have to wonder about why I don't see
> > anywhere near the left, center, right string
> > discrepancies that you do. While the pianos in
> > the university that I serve do go rather
> > drastically out of tune with the change of
> > seasons (abominable building) I still don't see
> > the unison problems that you do. Those kinds of
> > differences would make the pianos sound rather
> > hideous wouldn't they? I may get that much rise
> > and fall but it's mostly together over the three strings of the unison.
> >        I cannot dispute your observations about
> > the bridge pins but I also have to wonder if
> > tuning sequence plays some part in it or not. Do
> > you use any electronics? If so how do you use
> > them. If the piano is in a practice room would
> > you ever feel comfortable enough tuning from the
> > bottom up by machine and then checking the end
> > result aurally? Seems I remember that Al
> > Sanderson maintains that better stability is
> > achieved this way. Also, how are these strings
> > rendering across bearing points? If you tuned
> > with a temperment strip and then tuned in the
> > outside strings after setting bearings then you
> > could be setting up different tensions in the
> > wires even though they sounded fine when you were
> > done. This could be especially prevelant if the
> > strings weren't rendering all that well.
> >        I'll quit while I'm behind here and
> > patiently allow corrections from the list. Thanks fellas (and ladies too).
> >
> > best,
> > Greg
> >
> >
> >
> >
>
>_______________________________________________
>caut list info: https://www.moypiano.com/resources/#archives

Greg Newell
Greg's Piano Forté
mailto:gnewell at ameritech.net
www.gregspianoforte.com  
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