Picture a fiddle, a banjo and the American South and you think of white, hillbilly string bands. But the Carolina Chocolate Drops are proudly reclaiming another tradition just as ancient: the lost art of black string band music.

"It's been a casual yet epic journey we've been on," banjo player Dom Flemons said of his expressive young band, which opens for Crooked Still at Sanders Theatre in Cambridge on Friday, a concert that promises to be the string-band event of the year.