MODAL MINOR PENTATONIC
This configuration is sort of a mash up of the other two - the deleter and the single key diatonic - but is really a beast unto itself. Concept arose when I discovered that locking out a 6|9 chord on the deleter chromatic and then holding 3 delete buttons down would create a modal fifth drone within the 5 note (pentatonic ) scale, and that melodies could played by releasing one or more of the delete buttons.
The effect is unlike any other soundscape I had gotten out of the autoharp, and musically was akin to old-time frailing banjo players in "sawmill" tuning. Of course, the repertoire is limited. But it put me in mind to convert my Ron Wall Mountain 'Harp to take advantage of its pronounced bass presence due to the longer string lengths.
When no lock/deletes are used, it plays similarly to a single key diatonic. You can use the delete buttons to turn minor seventh chords into straight minors.
The details of the chord bar set-up is explained in this accompanying pdf. The bass is further enhanced in a-e drone mode by re-tuning #1 and #3 to e and a respectively leaving spaces cut in the felt. This all looks more complicated in theory than it is in practice, and is quite easy to play, since you are leaving fingers in place on 4 buttons and lifting.
The only video I have available at present is actually a further variant. Because the melody of I WONDER AS I WANDER contains 6 notes, I lock out just one note and hold down 4 delete buttons. You can hear me locking-on-the-fly after the first melody line: