[CAUT] SAT numbers

[Jeff Tanner]

On Aug 20, 2007, at 10:03 AM, Fred Sturm wrote:

> I came to believe, based on things I had read and conversations I  
> had had (which I'm afraid are hazy at this point) that Al Sanderson  
> had made a change to the FAC calculations to give more stretch to  
> the bass, in response to criticism by people using the SAT for  
> concert tuning.

Paul told me the curve had been recalculated for the SATIII, but I  
didn't realize it was for that reason.


> And I came to the conclusion that it was a "patch" that didn't  
> actually make any sense for pianos with an inharmonicity profile  
> that happened to have a plain wire, low tension F3. (Note that the  
> Hamilton 243 and the various flavors of Acrosonic are essentially  
> the same scale, somewhat foreshortened. But the smaller Acrosonics  
> happen to have wound strings for F3. Why should there be that much  
> difference in their tuning?)


I have tried using your idea at times and thought that the  
temperament section turns out funky.  It really does take a stretch  
of 18 or 19 for the temperament to work out right in the Hamilton,  
and in most cases I haven't thought the bass was too stretched  
either.  Using the numbers in the "library" for the Baldwin Hamilton  
doesn't work, because they are the "pre-recalculated" numbers.  Way  
too narrow.

But for scales like this, I often will instead resort to the F4  
tuning procedure.  I will go ahead and store an FAC tuning for the  
instrument, but then do an F4 stretch tuning from C3-F5.  The  
temperament section turns out so much nicer, and since the SAT is  
listening to the fundamental beginning at F#5 rather than C6, you  
don't get those squirrelly readings in that section like you do with  
the FAC tuning.  Then, for the upper octave and a half, I will switch  
back to the stored FAC tuning, or do it aurally, and for the bass I  
set the SAT for the 6:3 partial and readjust the cents setting as  
needed, but sometimes the FAC numbers work just fine in the bass.

Only thing to remember is that when using the F4 stretch, you need to  
remember the stretch number.  If you switch out of the memory mode,  
it seems the machine forgets the F4 and you have to recalculate it.

> (I had found that with those larger numbers, I was constantly  
> needing to intervene and narrow the octaves).
> 	I also always tuned the bass downwards (never started at A0) so  
> that I would know what was happening and be able to intervene.

The problems I've had with "intervening" is that I wind up with a  
whole string of affected notes that have to be changed just to make  
one fit better in one spot.  IOW, trading one compromise for another,  
or a whole bunch of them.  For example, D#3 might be wound, and  
doesn't work well with the scale of the plain strings in the octave  
above it, so we tweak it aurally to work better in the temperament.   
But that can set a whole series of problems with bass tuning  
beginning with B2, and all the other related notes going down in the  
bass, and it may well affect double octave and other coincident  
partials in the scales above the temperament.

I lost a long time tuning client over something similar after the  
church bought a new Yamaha GA-1 (or whatever that little 4'11" thing  
is).  Some member had decided it was a travesty that their church  
didn't have a grand piano and gave $5000 for the church to buy one.   
Nevermind that the Charles Walter studio they already had there was a  
much better piano and took up little space in the cramped choir loft,  
they needed a grand, and so the music director had to scramble to put  
the remainder of his budget for the year with the gift and buy a  
grand at the first opportunity.  It was about the third time I'd  
tuned the little grand after they'd gotten their freebies from the  
dealer when the pianist called to complain about two notes -- the two  
notes I had fussed over for at least 20 minutes or more trying to  
correct during the tuning.  The lowest two notes of the tenor section  
of this little grand, I believe C3 and C#3, are wrapped.  To get a  
clean octave with the octave above, absolutely nothing else in the  
scale worked out anywhere close with those two notes, and I simply  
could not tolerate the sound of the compromised chords when the  
octaves were clean.  It made the entire piano sound out of tune.  I  
had initially tuned it with the SAT, and tried to make aural  
corrections, only creating more problems with every aural  
correction.  I finally opted for compromising the octaves slightly so  
that other intervals worked better - coming back around to exactly  
how the FAC had calculated it.  The piano sounded better overall.   
But the pianist couldn't get over the sound of those two notes with  
their octaves, regardless of how bad everything else sounded if I'd  
tuned the octaves pure, even after I explained (on the phone) that  
the problem was in the design of that piano and that was the best  
compromise I could come up with.  I offered to come back and  
demonstrate, or try to tune some compromises that would make her  
happy, but she must have already made up her mind I didn't know what  
I was doing, and they haven't called me back again.  Had she been  
there and I been able to give her the option of where to leave those  
notes, I think she would have agreed with me.  There is no guarantee  
either that she was playing the piano at the same temperature and  
humidity as when I had tuned it.  That would have made it much  
different, too.

But the FAC was right.  It had produced a scale that was the best  
compromise overall, and the smallest of aural corrections just made  
things worse.  In my experience, this happens far more often than the  
reverse.  I find it to be a very rare occurrence that aural  
corrections are an improvement.

Jeff



Jeff Tanner, RPT
University of South Carolina



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