Different partials are used to tune different parts of the piano when using piano tuning software. The partials used are designed into the software. All tuning software systems therefore contain partial ‘changes’ as part of their tuning.
A partial change is the ‘switch’ from one partial to another within the tuning.
The location of these partial changes varies depending on the software.
Since every partial change is a potential tuning issue, the fewer the partial changes the better!
Errors at the partial changes, if large enough, will create an audible ‘hiccup’ in the tuning at that partial change. Partial change errors effect all intervals ‘spanning’ the partial change.
FAC partial change arrangement:
Partial changes are common to every ETD’s tuning system.
Since I’m an AccuTuner guy, I’ll use an FAC tuning as an example here, but errors at partial changes are common in every tuning system.
The FAC tuning partial arrangement is as follows:
The 6th partials are used for notes A0-B2
The 4th partials are used for notes C3-B4
The 2nd partials are used for notes C5-B5
The 1st partials (fundamentals) are used for notes C6 – C8.
The FAC tuning partial arrangement contains three partial changes:
3. and B5/C6.
Here is a graph of an FAC tuning. The partial changes have been circled in red:
(Click graph image to enlarge).
1. A two-partial change arrangement:
A standard FAC tuning uses the 2nd Partials from C4 to B4.
The partial changes in this two partial change arrangement are found between G#2/A2 and A4/A#4.
Instead of using the 2nd Partials in that range, the fundamentals or 1st partials are used from A#4 – C8. Eliminating the use of the 2nd partials in the tuning, leaves us with one fewer potential partial change error in the treble.
As you know, when A4 is tuned to A-440, the fundamental is being used. So there is no reason why the fundamentals can’t be used to tune A#4, and B4 and C5, and so on. There is just zero downside to using the fundamentals from A#4 – C8. And, as will be seen later, mapping the location for A5 is much easier when the fundamental is used at that location – rather than the 2nd P. of A5.
The tenor partial change is the other partial change in this two partial arrangement.
The partial changes locations in the two partial change graph below are in slightly different places as well.
This particular A to A partial arrangement provides a full two-octave range (A2 thru A4) with all notes using their 4th partials. No no partial change within that two octave range insures there is no partial change problem in the temperament area.
Another advantage to this A-A type partial arrangement, is that note A2 is generally found on the bass bridge for all by the longer scaled pianos. Using the same partial across the bridge break and the plain wire to wound string break, eliminates any partial change from occurring in that often challenging tenor are of the piano.
Using the same partials going down to A2 is especially helpful for the 26-bass scales, whose bridge break is between notes A#2/B2.
The partials used in the below chart are the 6th (green line) for notes A0-G#2, the 4th (red line) for notes A2-A4, and the 1st (blue line) for notes A#4-C8. (Click to Enlarge)
2. A one-partial change arrangement:
A one partial change arrangement is what is used in the Littau-Conrad Tuning System. This system uses the 4th partials from A0 – A4 and the fundamentals from A#4 – C8.
The only partial change in this arrangement is between A4 (4th) and A#4 (1st). This partial change location, between A4 and A#4, removes any possibility of an error at the partial change.
The use of the 6th partials have been eliminated which eliminated all partial changes in the lower half of the piano.
(Click to enlarge)
3. A 5-Partial change arrangement:
The above is just what you don’t want.
This partial arrangement has five partial changes with three of them in the lower half of the piano. No one is going to check and correct any of these partial changes. This partial arrangement might work on some large scale piano somewhere?
The larger pianos with their longer strings can be quite forgiving since their scaling is generally better. But this 5-partial change arrangement, used on anything but the longest pianos, could be problematical (many partial change ‘hiccups’) simply due to the number of partial changes contained in the tuning.
Many tuners using that system have mentioned they have to tune the bass by ear on many shorter scale pianos. Hopefully this post will help them understand why.