A new television documentary traces the roots of contemporary Chicago blues over several generations to rural Mississippi. Six Generations of the Blues premieres locally tonight at 8 p.m. on public television station WYCC. The two-hour special also traces the 30-year history of Earwig Music, where many elder statesmen of the blues have made their creative home—folks like Sunnyland Slim, Big Jack Johnson, the Jelly Roll Kings and David “Honeyboy” Edwards. The Earwig label got its start when founder Michael Frank struck up a friendship with Honeyboy not long after moving to the Windy City in the early ’70s.