Anyone following this thread should also be interested in another long-running discussion just reopened today:

TheGuitar and Irish Traditional Music

There's a nice link somewhere in there to an instructional website for the DADGAD-tuned guitar, how to use it effectively in a "trad" context not originally intended for the guitar.

Incidentally: the term "a capella" is pretty commonly used in the US -- I think that even non-musicians are generally familiar with the term, and don't consider it particularly pedantic or affected. There is a newish fad or trend on US college campuses for "a capella" singing clubs -- choruses of a dozen or members singing close harmonies without accompaniment. Freshmen apparently apply to multiple groups, are invited to join one, and maintain their membership for the rest of their four-year stays -- sorta like singing fraternities.