I really thought the most recent cover in the unnamed series of Bill Callahan/Bonnie ‘Price’ Billy singles might be the last one. For months, old friends Callahan and Will Oldham have been getting together regularly to cover other people’s songs, bringing a different collaborator along for every release. A week ago, the two of them shared their version of their late friend David Berman’s Silver Jews song “The Wild Kindness,” singing in harmony with Berman’s widow and bandmate Cassie Berman. But no. Callahan and Oldham are still going. They’ve got another cover out today.