“The Jazz Festival is the biggest marketing opportunity musicians have in New Orleans,” says Swedish-born vocalist/violinist Theresa Andersson. “You have so much exposure to people from all over the country, which is great when you’re a musician. ’Cause when you tour and you come to a new city, there’s going to be someone who’s seen you at Jazz Fest. The more you can do during Jazz Fest, the better it is. You can play a lot more shows during those two weeks than you normally can ’cause there’...