Joan Shelley and Nick Drake share a lot of qualities as vocalists, but mostly there’s an indescribable power in their hushed, calming tones that radiates a sharp sincerity. So, it’s fitting on Shelley’s new album of covers that the first song is Drake’s “Time Has Told Me,” a wise and poetic folk song with stark, soft instrumentation. It also sets the tone for a series of duets, including J.J. Cale’s “Magnolia” with Julia Purcell (where they switched out the “Makes me think of my baby, I left down in New Orleans” line with “Bowling Green”), and another where Shelley and Will Oldham deliver a haunting cover Dolly Parton’s “The Bridge.” Rivers and Vessels is a carefully-selected, well-executed 19-minute EP.