Errors at partial changes are common to all computerized tunings and computerized tuning software.

Because the Sanderson AccuTuner can ‘do’ Direct Interval Tuning, it’s the only Electronic Tuning Device that can ‘find and fix’ errors occurring at the partial changes.  

An FAC tuning has 3 partial changes- fewer than any other tuning software ETD.  And the AccuTuner is the only device capable of correcting them.

[Other software systems have as many as 5 partial changes!  The 3 in the lower half can be particularly troublesome – especially since their software (or hardware) has no way to correct them.}

This SAT’s Partial Change Correction (PCC) feature is in the SAT IV only, and is relatively new to the SAT IV’s programming.   If your SAT IV doesn’t respond to the STR + MSR command, it’s program may need to be updated.  You can do it yourself with a USB cable, a PC, the latest SAT firmware, and the ‘Updater’ program that came on the SAT DVD when it was shipped to you.  

To see if your SAT has PCC,  press and hold STO/Stretch and press Page UP a few times.   If you see ‘Partial Correction’ in the lower part of the display, your SAT has PCC.  If not, it needs to be updated to the latest program.   Contact Inventronics and they will send you the update and you can update it yourself via USB and your PC.

Here is a video for correcting just the Tenor Partial Change:

These partial change corrections can be done manually using an offset or with DOB.  The tenor partial change was the only one we corrected.

There are generally errors in the 2 treble partial changes as well.   The size and direction of those errors varied.  But those in the treble were really awkward to fix, even with a SAT.

Prior to PCC, the main point in measuring them – the errors –  was to prove they were there.   They can easily be measured with any SAT.

But now PCC makes it easy and fast to make sure all 3 of the FAC tuning’s partial changes are correct.

Once the corrections have been made, with PCC, they become part of the tuning.   This newly partial change corrected tuning can be saved and stored in your SAT for future use.

Please, please,  please consider making it a practice to lower the tenor partial change for every tuning!   Lowering the tenor partial change from B2/C3 down to G#2/A2 gives us a complete Two-Octave A-A Temperament range with all notes using the 4th partials.  PCC works anywhere on the keyboard, even if the partial changes have been moved!

The standard FAC tuning contains 3 partial changes.
Here are their default locations starting from the top down:

Since the PCC works in the ‘downward’ direction,  begin at the highest partial change:  B5/C6

Before beginning, you’ll need to know the correct setting for A4 – the setting for A4 @ A440.  To learn this, tune A4 to A440 and then measure the location of it’s 4th Partial.  That’s the setting for A4 @ A440.  Write down that number because you’ll use it later.


Start at the FAC tuning’s highest partial change: B5/C6

B5 is the highest note using the 2nd partials and C6 is the lowest note using the 1st partials.

After storing the FAC tuning as usual onto a page in SAT memory, go to C6 and look at the cents setting.
Now step up to C#6 and look at that cents setting.
Notice the cents difference in cents between C6 and C#6.
For example, if C6 is 4.2  and C#6 is 4.6, that’s a cents difference of .4 c.
So for this example we want to tune B5  .4 c. lower than C6, while using B5’s 1st partial.

Press TUNE and set the SAT to B5 @ 3.8  (.4 c. lower than the setting for C6)
Tune B5 to that setting.

B5 has now been correctly tuned.

Now press MEM and put the SAT on note B5.
Doing that puts the SAT back on to the page with the FAC tuning.   And of course, B5’s setting is known to the SAT.  B5 will be listening to the 2nd partial as usual on an FAC tuning.

Play the correctly tuned B5 on the piano and see if the lights are stopped.   If not, stop the lights using the cents buttons.

Once the lights are stopped, press and hold STR and then press MSR, then release both buttons.

That’s all there is to it.

Here’s what the STR + MSR command did:
The SAT knows the FAC tunings setting for B5 – both partial and cents, but the PCC really only cares about the cents setting.   Changing the cents setting by stopping the lights using the cents buttons on B5, tells the SAT there is a difference between the ‘stored’ cents setting and the cents setting in the display.   That cents difference is what PCC uses to correct the partial change.
Pressing STR + MSR tells the SAT to add or subtract whatever cents difference there is to all the notes below B5.    All notes below B5 will now have been either raised or lowered by the amount of the cents difference the SAT detected between the FAC setting and the tuning setting.

The B5/C6 partial change has now been corrected.

All notes C6 and higher remain the same, but all notes B5 and lower have been adjusted to correct the B5/C6 partial change.

(Yes, A4 has also been moved.   But don’t worry, we’ll put A4 back where it belongs later.   That too, is part of this routine)


Do the same thing at the B4/ C5 partial change that was done at the B5/C6 partial change.

Look at the settings for both C5 and C#5 and make note of the cents difference between those 2 notes.

For example:  If C5 is 2.9 c. and C#5 is 3.4 c.,  that is a cents difference of .5 c.

Press TUNE and set the SAT to (B4 @ 2.4) which is B4 being .5 lower than C5’s setting of 2.9.
Tune B4 to that setting.

Press MEM and go to B4 on the SAT.   This will put you back onto the FAC tuning.
Play B4 and see if the lights are stopped.  If they aren’t, use the cents buttons to stop the lights.  Once the lights are stopped,  press and hold STR and then press MSR, then release both buttons.

The B4/C5 partial change has now been corrected.    Both partial changes above A4 have been corrected.

If you are prone to looking at the numbers, to see what you’ve just done, you will easily see that C5 is still exactly as it was before making this B4/C5 partial change correction.   So is C6, C7 and all the other notes from C5 – C8.

But B4 will have been adjusted by the amount of the offset.   And so will all the other notes below B4 – all the notes from A0 – B4 will have been adjusted by the amount of the partial change correction’s offset.

Correcting A4:

Using PCC effects all the notes below the partial change corrected including A4.   In order for the tuning to end up @ A440, we need to put A4 back to it’s correct location.   

When using PCC to correct all the partial changes, the A multiplier default setting can be used as a way to slightly expand or contract the midrange – without necessarily worry about what it does to the setting of A4.   A4 will be corrected with PCC later so using the .8 A multiplier default to correct the placement of A4 is not longer needed.

I’d still recommend using the .8 setting for the A Multiplier because it reduces some of the stretch in the midrange of an FAC tuning.  Al Sanderson in his Two-Octave Direct Interval Temperament says that when the A2/A4 4:1 octave gets more than about 4 c. wide, A2 is probably tuned too low.

If you start lowering the tenor partial change down to G#2/A2, you will be able to easily see the setting for A2.  If A2 is using it’s 4th Partial and the setting for A2 is lower than -4.0. the A2/A4 double may be beating too much.   A2’s setting can easily be learned when lowering the tenor partial change, and it will often be lower than -4.0.

But if the .8 multiplier is used, A2 will not be as low.   I feel it’s a better place to start.   Now there ae so many SAT tools to tweak the widths of this area, DOB, the A multiplier, and even PCC, there are enough tools to make these adjustments and get a good sounding midrange.

The perfect A4 setting will be accomplished with PCC.   Different amounts of stretch can be applied to the midrange with different A numbers without having to worry about A4 not being at A440.

Using a lower A number will also effect the tuning in the treble and the bass as well as the midrange.   

Think of PCC as a ‘micro transposer’ for the whole piano.   PCC allows us to raise or lower the complete tuning by as little as .1 c.

Now you know why it’s so important to know exactly where A4 needs to be so you can put it there!

Correcting A4 is very similar to correcting a partial change – like pressing STR + MSR on B5 and B4.  To move the whole tuning up or down, just go to C8 and add or subtract the amount, and press and hold Sto/StretchNote and then press MSR/RST.   That’s all there is to it.

Now the A440 setting for A4 should be where we measured it earlier as the 4th P. of A440.

An Example:  Lets say that when we first got to the piano and tuned A4 to A440, the 4th partial is @ 9.3 c.
That is where setting of A4 should be on the completed FAC tuning: (A4 @ 9.3).

After adjusting both treble partial changes, A4 could now be almost anything.  It could be 10.3, or 7.9 or 8.9.

Compare where A4 is now to it’s correct A440 location of 9.3 c. gives us the amount and the direction of the the correction we’ll use to put the tuning back @ A440 for the tuning.
If A4’s ‘new’ setting is 10.3, we need to lower the tuning by 1.0 c.   If it is 7.9, we need to raise the tuning by 1.4 c.

To Correct A4, press MEM and go to C8 on the FAC tuning.

Change the setting on C8 by the amount of the correction and in the direction needed to correct A4.
Press  STR + MSR

Now look at A4 and it should be correct.   If not, just go back to C8 and make another correction the amount you need and press STR + MSR

Once A4 is correct, that’s done.

This can also be a another way the SAT can tune to non-standard pitch.  It can be done with PCC instead of offsetting the calibration, or using an offset, or whatever.   I’m sure clever SAT users will come up with more uses for this nifty STR + MSR function.

FAC  Tenor Partial Change Correction:

PCC does the tenor partial change just like the other 2.   The tenor partial change could be done first if desired.   Any changes made to it via PCC in the treble will be put back to A440 when the location of A4 is corrected using C8 and PCC.