If Allen Toussaint had only done a couple of things—say, producing the Meters and writing "On Your Way Down"—he'd still make any list of New Orleans' music immortals. As it is, Toussaint stands to be the most ubiquitous name in our 300 Songs series, for the sheer volume of essential music he was associated with as writer, performer or producer. Interestingly, his career began in 1958 with an album that didn't really foreshadow his career; either for the musical...