When John Mayer debuted at the turn of the century, curveball-throwing songs like the knotty “Neon” and the reflective “St. Patrick’s Day” hinted at his future guitar-god status. But he’s proven himself adept at crossing over into other styles, too: “Love Is a Verb” gently hums under twinkling Western skies, while the haunting Frank Ocean collaboration “Wildfire” is a spare, melancholic ballad.