No singing (that we know of), just speaking on Monday for Bono as he took part in a reception hosted by the Irish mission at the United Nations. Human rights and development were apparently the topics du jour. Norway's UN team posted a few photos from the event on Flickr, one of which we'll share below. (Thx to Ultraviolet Brazil for the tip.)
UPDATE: John Kingman has posted several dozen photos of Bono's appearance in this Flickr photo set.