Robert Conrad, Registered Piano Tuner/Technician, Tucson, AZ

Check/Correct All Partial Changes Using the SAT’s Partial Change Correction feature

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 piece of tuning hardware that can ‘find and fix’ error occurring at the partial changes.  None of the iPhones,  iPads, or Android devices can do Direct Interval Tuning.

Being able to correct partial changes is unique to the Sanderson AccuTuner.  An FAC tuning has fewer partial changes (3) than any other tuning system,  and yet the AccuTuner is the only device capable of  correcting them.

[Some computerized tunings from other software systems have 5 partial changes built into them, with 3 of them being below A4!   Each of those partial changes will more often than not, contain a partial change error.]

This Partial Change Correction (PCC) feature is relatively new to the SAT IV’s programming. So if your SAT IV doesn’t seem to be responding to the STR + MSR command it’s program may need to be updated.

[To see if your SAT can do this, press and hold STR and press Page UP a few times.   If you see ‘Partial Correction’ in the lower part of the display, your SAT is ready to go.  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:

We used to have to do these corrections manually with an Offset or with DOB.   Most of the time the tenor partial change was the only one we corrected.

Every time I measured one of the treble partial changes, there were always errors.   The size and direction of those errors varied.  And generally speaking the treble partial changes were really awkward to fix.

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, with a little know how and tuning of one note at each partial change, and then with the pressing of only two buttons, the SAT IV can easily correct all partial change errors.

Once the corrections have been made, they are part of the tuning.   The ‘new’ partial change corrected tuning can be saved and stored for future use if desired.

And, for those of us who lower the tenor partial change so we can have a complete Two-Octave A-A Temperament range all using the 4th partials to make all our aural tweaks and adjustments, the Partial Change Corrector (PCC) works 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

Also, before beginning, either Tune A4 to A440 and measure the location of it’s 4th Partial, or make note of the starting setting for A4 on the FAC tuning!  You’ll need to know the correct setting for A4 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 the .8 A multiplier default (recommended) for the FAC calculation, A4 will be very very close to A4.   If the .8 A Multiplier default was used to calculate the FAC tuning, the FAC tuning’s setting for A4 can comfortably be used for this.

However, if the .8 A multiplier default was not used, the FAC setting for A4 may be off.  This is the time to correct that so the tuning when completed will have A4 at exactly A440.

PCC can give us even more control over our tunings with this ‘Correcting A4’ step.   The purpose of the .8 multiplier is to put A4 closer to A440.   What the  .8 multiplier does is basically just use a lower stretch number tuning in the midrange  – for the ‘A’ part of the FAC tuning.   Most of the time that less amount of stretch is good, but now that we can so easily remedy the location of A4, we have yet another option.  If desired,  the SAT default multiplier of 1.0 can be used instead of .8 because we can always put A4 right on a440 by using the A4 correction which is part of the PCC procedure.   What this means is that different amounts of stretch can be applied to the midrange with different A numbers without having to worry about A4 not being at A440.

When the FAC tuning is calculated, each of the factors, the F number, the A number, and the C number are all related to each other.   Using a lower A number effect the tuning in the treble and the bass as well as the midrange.   

What PCC has inadvertently given us, is a way to do practically anything we want to do FAC-wise when it comes to using different FAC settings – regardless of whatever FAC numbers used, after correcting the treble partial changes, we can put the whole tuning dead on A440!

Do this first:  To make sure A4 ends up @ A440, tune A4 to A440 and measure where A4’s 4th partial is.   (After tuning A4 to A440, set the SAT to A6 and play A4.   Stop the lights using the SAT buttons).   That’s the setting for A4.   Write it down because that should be the setting for A4 when tuning the piano.

Even if the .8 A Multiplier Default is used, comparing the two may indicate a couple tenths one way or the other.   If not using the .8 A Multiplier Default, this A440 setting for A4 should be used to put A4 to the correct location.]

Correcting A4 is very similar to correcting a partial change – like pressing STR + MSR on B5 and B4.  Note C8 on the FAC tuning and PCC will be used for correcting A4

The new setting for A4 is where A4 is now, after doing the 2 partial change corrections above it at B4/C5 and B5/C6.

The A440 setting for A4 is where we measured it earlier as the 4th P. of A440.
Or, it is the original setting for A4 after using the .8 multiplier and calculating the FAC tuning.

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 the treble partial changes above A4, A4 could now be almost anything.  It could be 10.3, or 7.9 or 8.9.

Comparing where it is now to it’s correct A440 location of 9.3 c.  gives us the amount and the direction of the the correction we need to make so that A4 will be @ A440 when the piano is tuned.
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.

Since these partial change corrections only effect the notes below the corrections,  C8 is exactly the same as it was at the beginning.   Of course the setting for C8 doesn’t matter, but C8 is used to put A4 back to it’s original A440 position.

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.

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