Greetings:

I have generally heard the term "mountain modal" apply to the 5-string banjo tuned (5th to 1st) g-d-g-c-d. Note that the only difference between this tuning and standard G major tuning is that the 2nd string is raised half a step to c. You can likewise think of it as G minor tuning with the 2nd string raised a whole step to c.

You then play using g as the tonal root. Since the chord lacks the third note in the scale, it is undefined as to whether it is a G major or G minor using common designations for modes, thus it is a "modal" tuning. However, the addition of the c note, the fourth, gives the chord its distinctive "mountain" sound.

By stopping the 2nd string on the 2nd fret [o-o-o-2-o] you make a chord that comprises only g's and d's, and thus can be used as a tonic in either G major or G minor, but which lacks the "mountain" sound. Other useful chords are as follows:

[o-3-o-o-o] G mountain modal 7th: adds an f note to the bass.

[o-3-2-o-3] F major with a high g drone: a typical mountain modal chord.

[o-o-2-2-o] D modal with a high g drone: can be used whenever a D major or D minor is required.

[o-o-2-o-o] D modal 7th: as above but with a c note added.

[o-2-2-1-2] A7: our old friend!

[o-2-2-o-2] Am7: our old friend's minor cousin!

Some tunes to try: Shady Grove, Pretty Polly, Lady Margaret, Shalom Chavarim.

That should get you started.

--- Steve