Charlie, Mixo is a scale type, not a key. Modes can start on any note. We play Cold Frosty, Kitchen Girl, Old Joe Clark in A Mixo, Home with The Girls in D Mixo. I have no clue about the relationship of banjo/guitar tunings to modes......my guitar player always uses Standard tuning, and then chord shapes to fit the scale.......somewhere there is a thread called Modes for Mudcatters. (I think that is the title. Great piece of work, and explains it very well)