Here is a simplified temperament plan for single key of C

STEP     1 do    2 re     3 mi     4 fa     5 sol     6 la    7 ti

NOTE     c          d          e            f         g           a        b

CENTS   0        -2        -5           0         0         -5      -5

So, the 1-4-5 steps , which are the tonic notes for the I- IV - V chords, are at zero on your meter. Consequently, you will be at the same reference point as others in an ensemble. The rest of thenotes are adjusted to sound "sweeter" on the autoharp, but not so much as to noticeably conflict withequally tempered instruments.

Here is the same thing, as it is more conventionally shown, vertically

STEP     NOTE IN KEY OF C        CENTS

1                     c                                     0

2                     d                                  -2

3                     e                                   -5

4                     f                                     0

5                     g                                    0

6                     a                                  -5

7                     b                                  -5