"Folk music" is probably even harder to pin down than "new age", there is so much variety. A folk style that I would like on Real Tracks is the 50's - 60's folk revival style typified by the Brothers Four, Wayfarers, Kingston Trio, etc. There was a strummed banjo style that was unique to their sound.

Other good folk banjo styles are clawhammer and Pete Seeger's uppicking. Scruggs and melodic styles are more popular but not very folky sounding.