Billy Justineau’s keyboards bring an extra splash of Americana into the countriest of cuts. Whether he’s leaning into the organ on the Brothers Osborne’s larger-than-life country rocker “Stay a Little Longer,” giving Charlie Worsham’s tender “Sugarcane” some extra down-home sweetness, or lending grit to the honky-tonk stomp of Lainey Wilson’s “Neon Diamonds” with rolling piano licks, Justineau makes it all sound as natural as falling off a log.