During a trip to WNYC's Soundcheck in anticipation of his Age Of Adz shows at Prospect Park, Sufjan Stevens performed "Pleasure Principle," the final pretty bit of 25-minute Adz closer "Impossible Soul." The National's Bryce Dessner and two backup singers joined him. [videoembed size="full_width" alignment="center"][/videoembed] You can stream the whole performance at wnyc.org. Those Prospect Park shows take place 8/2 ...