No other city can lay claim to as many unsung musical geniuses as New Orleans. It’s caused by the same combination of provinciality and miscegenation that makes the city such a fascinating place to live in. (Meaning, it’s a musical melting pot that has a hard time providing for its musicians.) Indeed, the Jazz Fest itself works because it’s the greatest array of talent that lies just outside the radar of the national consciousness.

Irma Thomas reigns unchallenged as the city’s Queen of Sou...