measuring FAC on SAT

[Jim Coleman, Sr.]

Hi Terry:

You were wondering why Inventronics or Coleman had not mentioned taking 
the measurements of FAC without tuning the notes first.

As a matter of fact Dr. Sanderson has shown this to be more accurate and 
has demonstrated this many times. The one precaution to take is that you 
must eliminate the offset before doing the rollover to calculate the 
tuning, otherwise the tuning will be at whatever pitch your last reset 
was made. One reason the reset method of measuring the FACs is more 
accurate is that we have difficulty tuning to the accuracy of .3 cents 
whereas, we can measure to within .1 cents.

One other comment I'll make while I have the floor is that if one 
measures the FAC numbers while the piano is 1/2 step flat, the 
inharmonicities of those 3 notes will be higher.

For example, I measured the A4 stretch number of an Acrosonic spinet to be
8.2. Then I tuned the note 1/2 step flat, reset the A4 to that pitch for 
its A5 reading, then measured the stretch number at A6. It became 9.1.
That is quite a difference and will give a different tuning. As a matter 
of fact it will be very close to a pure 5ths Equal Temperament.

Jim Coleman, Sr.

PS Just last week in a post about using the old F4 single stretch number 
with the SAT III, I mentioned measuring the F4 stretch number without 
first tuning the F4 as long as the pitch is fairly close. To date, no 
one has mentioned anything about that post which I thought in some 
respects to be revolutionary. Should I post it again? Maybe it was not 
considered worthy of comment. Perhaps I was too telegraphic in my 
descriptions.