“I bet this song make no sense to you,” Pharrell Williams sings on “God Bless Us All,” and it’s difficult to imagine him sounding any less worried by that fact. Like N*E*R*D’s three previous albums, Nothing collects all the zany ideas that Williams and his Neptunes partner, Chad Hugo, couldn’t convince their production clients to try: schmaltzy Love Boat horns (“Perfect Defect”), fuzzy psych-rock guitars (“Help Me”), even a lengthy sample of congressman Patrick Kennedy flipping his shit on the House floor (“It’s in the Air”). Nutty? Yes. Compelling? Occasionally.