Sturgill Simpson might be gearing up for his own tour as Johnny Blue Skies & the Dark Clouds this fall, but he joined the Black Keys Thursday night at Nashville’s the Pinnacle for a cover of the soul classic “I Heard It Through the Grapevine.” The Keys were also joined by Marcus King for a cover of Willie Griffin’s “When There’s Smoke, There’s Fire.” Contrary to previous rumors, Simpson and the Black Keys frontman have not previously collaborated. But Johnny Blue Skies & the Dark Clouds’ new LP, Mutiny After Midnight, was recorded at Auerbach’s Easy Eye Studios in Nashville. Auerbach and Simpson also both shared a close relationship with the late John Prine.