“Ever since her days with folk revivalists Carolina Chocolate Drops, Rhiannon Giddens has championed the marginalised or suppressed elements of American musical tradition. Now artistic director of the Silkroad Ensemble, a multi-ethnic, 13-strong troupe founded in 2000, Giddens has overseen a history of America’s coast-to-coast railroad, or more particularly the army of workers who built it. Most we”