He didn't say a word beyond introducing his band. But he sang the baleful "High Water" and the not-so-carefree "Watching the River Flow"; he sang "Lonesome Day Blues," with lines like "The road's washed out — weather not fit for man or beast." When he sang "Positively Fourth Street," it sounded like an indictment of the government's response to the hurricane; when he closed his set with "All Along the Watchtower," his band played power chords like warnings of the apocalypse.

Mr. Dylan, who recorded his album "Oh Mercy" in New Orleans in 1989, wrote about the city in "Chronicles, Volume One," his autobiographical book. "There are a lot of places I like," he wrote, "but I like New Orleans better. There's a thousand different angles at any moment." He added that it was "a great place to really hit on things."