Allen Toussaint and I were walking across the lobby of a fine but nearly deserted hotel, located just across Canal Street from the French Quarter. An older gentleman had just entered the rear door and was coming toward us when he recognized Allen and stopped in his tracks. His grim expression lit up. He became elated and emotional, grasping and shaking Allen’s hand vigorously, as if his very presence were a sign that all was not lost in the shattered city. He didn’t speak at first, but his expression said, “If you are back, then we are all back.” I had never doubted that Allen was a prince in thin disguise. – Elvis Costello, writing in his 2015 book “Unfaithful Music & Disappearing Ink.” His collaboration with Mr. Toussaint, 2006’s “The River in Reverse,” was nominated for the Best Pop Vocal Album Grammy award that year.