CTE-Master Tuning

[Fred Sturm]

Avery Todd wrote:
> 
> Fred,
> 
> I think what people are talking about is that with humidity changes, the
> piano can change, thereby affecting the FAC numbers, thereby affecting
> the "Master Tuning", in this case. This has been being talked about
> lately on the pianotech list about the climate changes changing the FAC
> numbers somewhat.
> 
Avery, 
	One of the basic features of the FAC is the choice of partial it tunes
by. Dr. Al found that by tuning the 4th partial, thirds would progress
nicely (because the third is produced by beating between 4th partial of
the upper note and 5th partial of the lower). So all that is needed is
for the numbers to progress evenly to get smooth thirds. Hence, even if
the "A Number" shifts, the thirds will still progress well. All that
will be affected is the width of octaves, and the pitch of A4. (It's a
bit complicated, but this is basically true).
	The only place this doesn't work is over bad inharmonic breaks, where
inharmonicity jumps. But test pianos shouldn't have such bad breaks. For
these reasons, I am very skeptical that humidity would cause a piano to
change in such a way that thirds tuned to the same numbers wouldn't
progress the same. (The tuning test uses different - lower - partials
than the FAC program, but still, I find it hard to believe that humidity
change would have such an affect. Unless conceivably the bad
progressions happen over an octave break, particularly B2 to C3,
possibly B3 to C4 and B4 to C5.)

Joe Goss wrote:
>Hi Fred,
It is possible to change the SATll  program numbers of a FAC tuning and
not
know that they have been changed. Only a hard copy will verify the
correct
numbers.
 I know this to be a fact because a few years back when I was using the
canned tuning programs and using the offset to a different pitch,
several of
the programs that were being used a lot suddenly were not giving a smoth
progression and had to be reprogramed.

Joe,
	Well, I don't know precisely how the SAT's interiors work, but I
believe that numbers inputted into memory stay the same. That is,
individual cents numbers entered to memory for individual notes on
individual pages of memory. (They'd better, or I want my money back ;-)
) 
	Test tunings have nothing to do with the FAC program. THe notes are
simply read, and then entered one by one into memory on a particular
page that is there for the purpose. So there shouldn't be any
calculation by the machine (other than creating the associated pages,
like Detuning. But that's just simple arithmatic based on the original
input numbers, applying them to a separate page of memory). 
	Unless someone actually goes to the page on which the master tuning is
recorded and changes individual notes, I don't think there is any way
they can get changed. I don't think you could even enter an FAC into
that page of memory - it's pre-programmed to accept only individual
entries at particular octaves. Trying to be fool-proof.
Regards,
Fred Sturm
University of New Mexico