The Gascon bastide, or fortress town, of Marciac was founded in 1298 to keep out the brigands infesting the local marshes. All for naught: seven centuries later, the town is infested (just two weeks a year, but still) with jazz musicians. “Jazz” construed broadly: the current incursion includes Ahmad Jamal, Gregory Porter, Melody Gardot, Gilberto Gil, Angélique Kidjo, Roberto Fonseca, Chick Corea, Cécile McLoren Salvant, Sting—the dizzying list goes on—and the usual suspect, Wynton Marsalis. —E.E.