Veteran bluegrass/folk string player Peter Rowan, 70, returns to the main stage with support from acclaimed Atlanta combo the Mosier Brothers. Rowan began his career as a guitarist and lead singer in Bill Monroe’s Bluegrass Boys. He collaborated with mandolinist David Grisman in the flexible Earth Opera before co-founding Old and in the Way with Jerry Garcia. Rowan’s latest disc — a 13-song collection of originals and traditionals titled Legacy — demonstrates some unusual reggae and world music influences. Local combo Portside Still — featuring Steven Sandifer (of Dangermuffin), Walter Biffle, Keith McCullough, and Bob Sachs — picks and strums a variety of folk styles on the deck from 5-9 p.m. Doors for the main stage show open at 8 p.m. and music starts at 9 p.m.