I have heard this term used with the banjo, but do not know the notes the banjo strings require. I am not sure if it is the same as mountain minor which also is used in the Ozarks on the banjo. Surely someone on Mudcat will have that information. It is an open tuning with a distinct sound. The modal tuning on an autoharp might be a little tricky. Drew Smith, who has some autoharp instruction books and tapes available is able to achieve a modal sound on the autoharp. He is an excetional player with a real fondness for American folk tunes and songs. Evo Bluestein is another autoharp player who uses a chromatic harp a lot and can achieve some interesting sounds with chord bars.