When Harry Shearer was asked what he misses most about post-Katrina New Orleans, he answered in two words: Henry Butler.

Butler is one of many of the city’s great musicians who have been displaced since “the flood” as he refers to it; he’s a member of the all-star group of local exiles, the New Orleans Social Club. Like most of his peers, Butler misses the city even more than it misses him simpl...