[CAUT] SAT numbers

[Fred Sturm]

Hi Avery,
	Yes, it was I. I generally defaulted to an 8 - 10 F number when it  
was higher as read (I now use RCT).
	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. 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?)
	In analyzing the numbers, I simply couldn't come up with a reason  
for the portion of the tuning produced by the F number (it affects  
the bottom 2 1/2 octaves, and only to a certain extent). It would  
make some sense if, say, F3 were taken as the 6th partial of A#0  
(extrapolate the 1st partial of F3, and use it to create a curve as  
the next to lowest of the 6th partials tuned). But it sure didn't  
seem to work that way. So I just started doing the default thing, and  
found that the curve produced worked quite well most of the time (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  
simplest way of "keeping and eye on things" was to play the notes a  
5th and an octave above the note to be tuned (from time to time, no  
necessarily every single one), which would tell you how wide or  
narrow the 6:3 octave and the 6:4 5th would be (before tuning the  
note itself - meaning its 6th partial). If the 6:3 was going to be  
significantly wide (lights rotating sharp more than a bit), I'd  
change the setting until, as I recall, the octave above made the  
lights rotate just sharp, while the 5th made them rotate just flat.  
And then, of course, the ear decided if the note was "right" once  
tuned (keeping in mind that "right" is a vague notion on many of  
these beasts, with lots of conflicting reasons to go one direction or  
the other).
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu



On Aug 17, 2007, at 7:41 PM, Avery Todd wrote:

> List,
>
> I have a question about high numbers on F on an SAT III. I tuned  
> two Pearl River UP 115's today (studio size) and one of them had an  
> F number of 15.1 and the other had 14.9. I was getting way too much  
> stretch as I went into the bass so I just ended up tuning them  
> aurally!
>
> I seem to remember that someone (Fred Sturm?) mentioned some time  
> back that he never uses a number higher than ?????. Am I correct?  
> Or was it someone else? Just wondering what others of you SAT users  
> do in a case like this. BTW, this is a VERY good reason why it's  
> good to also be able to tune aurally!!!!!!! :-)
>
> Avery Todd

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