Back in Grandpa’s day, jazz groups regularly looked to the pop charts for material. And that was The Bad Plus’ conceit when the practically perfect trio consisting of Ethan Iverson (piano), Dave King (drums) and Reid Anderson (bass) began recording together in 2001. After four albums of original music, the Plus returns to Plan A with It’s Hard, an album of sensationally reimagined material like Cyndi Lauper’s “Time After Time,” Kraftwerk’s “The Robots” and Peter Gabriel’s “Games Without Frontiers.” Rather than merely soloing over changes, the trio refracts the originals through their own colorful, sonic kaleidoscope.