You couldn’t write a history of American music without a solid chapter on Bonnie Raitt. From her roots as a blues guitarist, she’s created a gorgeous melange of rock, R. & B., blues, folk, and country—helping to establish a new category now known as Americana. But she’s far from resting on her laurels; her latest album, “Just Like That . . . ,” is nominated for four Grammy Awards this year, including Song of the Year—a category in which her competition includes Beyoncé and Adele, stars a generation younger than Raitt. She talks with David Remnick about her early career in the blues clubs of Boston; the relationship between older Black artists and the nineteen-sixties generation of younger white afficionados; and the state of the genre today. “The way that blues and R. & B. and soul music [are] interwoven with so many different styles now . . . the cross pollination of influences that streaming has made possible—it means that blues is always at the root of whatever funky music is out at the time,” she says. Raitt also reflects on how finding sobriety in her forties changed her music. “I think a lot of us are busy putting on a big persona—proving ourselves in the world—for the first two decades of our careers,” she says. “I became more who I really am at forty-one than I was at thirty-one.”