Armed with his trusty, busted acoustic guitar, Trigger, Willie Nelson has made a profound mark with his unvarnished country tunes. Covers of the Red Headed Stranger’s greatest—like Chris Stapleton’s lonesome “Last Thing I Needed, First Thing This Morning” and Patsy Cline’s timeless “Crazy”—abound. But he’s also always been a crack collaborator, as “Good Hearted Woman,” his down-home duet with Waylon Jennings, testifies.