Tips For SAT Users

[Jim Coleman, Sr.]

Special help for SAT users

The newer Sanderson AccuTuners (SAT for short) have the (FAC)
capability for predicting or calculating a tuning for a piano.
Although the measurements of F3, A4 and C6 will provide
a very good tuning for most all pianos, one may alter this 
tuning to suit one's personal preferences. For example some 
Technicians prefer to have their octaves very tight while others 
prefer to have a little stretch in the octaves. Measuring the 
3 notes gives the instrument a pretty good idea of the slope of
the inharmonicity of the piano, but it does not tell everything
about the bridge shape or where the string sizes or type change.
Originally there was a program for measuring 6 C's of a piano
to predict the tuning, but here again, wire size changes and
bridge configurations were not known to the program. One could
measure the inharmonicity of every note on the piano, but this
would be tedious and impractical to do for each tuning job. As 
a result Dr Sanderson came up with the scheme to measure only
3 notes to still get a pretty good representation of the tuning
requirements for a particular piano.

If a treble bridge has a hockey-stick like bend at the bottom
It is likely that some additional stretching could be advantageous
for the tuning of this piano. I am indebted to Kevin Ramsey 
for this simple way of determining if additional stretch should
be welcomed. Here is his procedure:

After measuring and computing a tuning for a piano using the 
FAC capability, carefully tune the A4 to the SAT. Then press
Dn/OCT to A3, play the A4 again and notice the direction of the
LED's. If they are stationary, you would have a tight 4-2 type
octave when the A3 would be tuned to this setting. This means 
that the second partial of A4 is exactly in tune with where the
4th partial of A3 will be when it is tuned later. This is quite
understandable when you realize that the SAT (FAC) tunings tune 
by the 4th partials of each note from C3 through B4. When the A4
is played while the SAT is on A3, it is the 2nd partial of A4
which is being viewed on the display. When the display is set 
this way for the tuning of A3 later, its 4th partial will be
tuned to this setting. In essence you will have a perfect unison 
between the 2nd partial of A4 and the 4th partial of A3. This 
would give you an aural test where the M3rd F3-A3 would beat at 
the exact same speed as the F3-A4 M10th.

If on the other hand the LED's are rotating counterclockwise in
the above example, the octave would be narrow when the A3 is 
later tuned to the A3 setting. This would result in an aural
test where the M3rd would be faster than the M10th. This would
indicate that we would need to stretch the tuning more.

Additional stretching can be done in two ways. For those who 
have the SAT III, the blue SHIFT button is depressed while the
Up/CENTS button is pressed 2 or 3 times to stretch the tuning
by .3 beats per second (bps). This will give the A3 a lower
cents setting while the A4 setting will remain the same. In 
most cases this will at least make the 3rd-10th tests equal 
or better. On some pianos one might wish to add a little more
stretch by increasing the Double Octave Beat control (DOb) to 
.5 bps.

For those who have the older SAT II or SAT I with the FAC 
capability, they can increase the value of the A4 Stretch 
number by perhaps .5 to .7 cents to accomplish the same thing.
However it is important to remember when you get up to C5 in
the tuning process that it is necessary to add the same amount
to a reset of the instrument's pitch by using the SHIFT and
RESet buttons. Two articles in the PT Journal of Apr and May 
in 1997 explain this in greater detail.

It has been noted for several years that the better tuners 
prefer to stretch their octaves at least to show a half bps
difference between the M3rd F3-A3 and the M10th F3-A4 with 
the 10th being the faster. This can be easily duplicated 
using the SATs.

For those still using the older single F4 Stretch number 
system Rick Baldassin wrote an excellent piece on doing a 
similar thing for the SOTs and the early SAT's. In this case 
the reset additions need to be made between F4 and F#4.
If there is enough interest, it might be possible to get him 
to repeat that for us here on pianotech.

Jim Coleman, Sr.