Chromatic Setups Table
chart revised 7/15/09
The above link will display a table of various ways to tune the chromatic autoharp in order to serve different sets of keys. The context was for meantone tuning and for the presence of three dim7 chords on a 21 chord. Therefore, only 6 keys are shown for each tuning.
The table applies only to bass strings 1-13. All the other strings (from #14 upward) are tuned standard, two complete octaves from C to C to C plus any 37th string, typically a D.
Four keys on each would be quite satisfying. The two keys in brackets would be the sweet spot keys, the instrument's strengths and the ones a player is likely to favor.