I may have to rename this web site The Arcane Autoharp because I will be going down some pretty deep rabbit holes. But many of those visiting this tuning section will just be interested in the bottom line, which is represented by the values shown in the various tables linked underneath. DISCLAIMER: whereas the "sweet" tuning temperaments detailed here are my best suggestions, they are not presented as indisputable truth but in fact are considered opinion based on years of hands-on experimentation with the autoharp, as opposed to generalized music theories meant to apply to all instruments. The point being, I am thinking in terms of chords rather than scales, that when you press the button, one just hears notes that are opened. With a guitar, piano, etc. all the possible note combinations or intervals are to be considered. If you are interested in the thought processes involved in arriving at the temperament I use for my Perfect Fifth single key diatonics, you can dip your toe into the treatise I wrote, but you might want to have some of those thigh-high wading boots.
Here is the operative quote from the "treatise":
“If you assume that it’s more important to have certain chords in better tune than others, you can favor those with sweeter intervals. (By extension, in a chromatic autoharp setup - some keys are more important, some chords within those keys are more important, and some intervals within those chords are more important – and the tempering can be adjusted accordingly.) What results is that, when you play a musical piece, as the progression moves away from the harmonic center, the chords become less “in tune”. A dissonant tension is created and is subsequently resolved when you return “home” to the I chord at the end of the piece, as most musical compositions do.”
The temperaments presented are shown just for particular key(s), and of course can be transposed to whatever starting point you need. I made a color-coded transposition chart for the standard autoharp keys, but it can be used for notes as well.
That being said, if you are of the persuasion that for your purposes, or for simplicity's sake, or because you have a 10 key autoharp, or for whatever reason you want to use equal tempered tuning (i.e. all notes to zero on your meter), that's fine with me. Really.
However, be advised that not making a choice is still making a choice, and you are opting for certain inherent compromises in the tuning of your instrument. To me, one of the advantages of the autoharp is that it is possible to tune it to make the chords sound better than they do on other instruments. That is to say: more aesthetically pleasing to the ear. (I do not wish to engage in the discussion here about where and when to make compromises - I am merely referring to the mathematical fact that a Perfect Fifth is a string vibration ratio of 3:2 ---- and therefore, if you tune c and g to zero on an electronic device, the g is actually 1.91 cents flat according to that ratio).
To be fair, the fifths derived from equal tempered tuning are really quite good, especially when heard in chords that use two of them (like Am7 c-e-g-a) or three (like C 6|9 c-e-g-a-d).
Anyway, if you care to delve into my reasoning and voyage of discovery, I am linking to a pdf of my TREATISE ON AUTOHARP TUNING, which grew out of a workshop I did for the Augusta Heritage class in 1988 at Elkins WV. It was updated some over the years, especially in 2006 after physical experiments partly inspired by an article - that I read once in the 1980s and had a concept which stayed in the back of my mind - by the late Woody Padgett in Autoharpoholic Magazine. Please note that this was written off and on over 30 years and the specific numeric variances from zero cited are somewhat arbitrary and different from one schedule to another. The important part is that the relative pitches, sharp or flat, are consistent, and that is the point. So if interested, CLICK HERE .
Other pages in this section detail the "sweetened" temperament settings for various configurations: 2 key Diatonic, 3 Key Diatonic, 4 key Chromatic, 1 key Perfect Fifth, and 1 key Simplified. Again, they are given a key/scale to illustrate but can be transposed to any other key. However, in my system, the tonic, sub-dominant, and dominant (i.e. I,IV,V) notes are all set to ZERO. This allows accompanying other instruments and vocalists without conflict. I understand that contradicts the conventional wisdom. So be it.
Note that, technically, a two-key diatonic is a contradiction in terms, but is generally used in autoharp circles for a string schedule with 8 different notes and chords that can be made from them. Some people have lock bars which can be engaged to block out the one note outside of a one-key diatonic scale, aka do-re-mi, etc. , so it may be played in an open-noting style. Same goes for the three-key diatonic. The OS factory standard "chromatic" autoharp really is only good for 4-5 keys, although some have modified their instruments to accommodate more keys. Of course, those would tend to favor a straight-up equally tempered approach to the tuning.
I assume most people just want to get to the temperament schedules. I might point out to those who say they cannot hear a difference between equal and "sweetened" tuning that they perform the following short demonstration. Select 3 notes from a major triad, any major chord will do, but for this case let's just take c-e-g, and, for these purposes, in your middle octave. Tune the c,e, and g to zero. Either pluck the 3 strings together or hold down the chord bar and strum. LISTEN. Then loosen the e string so it reads 5-12 cents lower on your tuner. Again, sound the 3 notes simultaneously and LISTEN. The latter chord should sound more harmonious, sweeter, "better"; the former, equal tempered, chord will seem harsher, more strident, tenser. That is essentially the phenomena at the heart of the matter, and for at least 600 years, has been the subject of endless and heated discussions as to how to best deal with it.
This is HOW I DEAL WITH IT.