Jessica Simpson is sitting on a thrifted green banquette in her Nashville music room, wondering if Sister Rosetta Tharpe is trying to send us a message. We’d been talking about the late godmother of rock & roll, who Simpson just described as “the most badass” of all potential badasses, when the silver resonator guitar behind her rung out a dissonant note entirely on its own. Was it contact from the great musical beyond, or just Simpson bumping the neck against the window? Who even cares either way? Simpson, after more...