This is an arrangement of Duane Allman's "Little Martha", arranged for 5-string banjo.
My banjo was tuned down to an open E chord... It's exactly the same as a standard G tuning, but lower in order to achieve the original key of E and make the arrangement playable in the easiest possible way.
I would say this is a fairly challenging piece to play, because of the 'up-the-neck' parts.
Also, you can leave the lowest pitch note off of ANY 4-string, closed-position chord in the arrangement to make the chords just a wee bit easier to finger at higher speeds.
Tom