Mick Jagger’s illness that forestalled the Rolling Stones’ tour, and thus their big gig at the New Orleans Jazz and Heritage Festival, came as a letdown for fans, notably baby-boomers, holding $175 tickets. But, in the scheme of time, the loss will fade like a yellowed husk at the edges of the cornucopia of music in the festival’s 50th year.

At least the Stones’ punt furnishes a greater potential spotlight on grass roots talent slated that day. Like Glen David Andrews, the swaggering trombonist and high-octane vocalist of gospel plus more, a showstopper to his toes. For many acts like Glen David’s, which draws people to Frenchmen Street and Tremé venues, the festival holds the chance for expanding the fan base. So it did in the 1980s when the Neville Brothers (who once fronted for the Stones under a full moon in a Barcelona bull ring) rolled out the fire as the final act, playing that slot for years thereafter. Trombone Shorty picked up that torch with Big Freedia angling in the wings.

On the same no-Stones day, Mavis Staples the gospel-pop diva, carrying the legacy of her departed siblings who sang under the late Pops Staples, is an American treasure. With her glorious pipes she spurned the matrimonial offer of a young Bob Dylan, decades before the Nobel committee gave him the literature prize in a cultural gulp moment, on the heels of which its judges reeled from a Scandnavian sex scandal. Mavis, we love you forever and a day.

Aaron Neville, the singer with that honey sweet falsetto that soared in the Grammy-winning duets with Linda Rondstadt, whose performing days are done, plays the fest on May 4. Aaron is 78, and as witness to his festival acts over the last decade, I marvel at his vocal agility and how a dude with the fullback’s heft has managed to age so gracefully.

Of the rhythm-and-blues artists who provided the soundtrack to a post-war generation, Aaron, Irma Thomas and the ageless Deacon John stand out equal parts charm and resilience. We offer a bow to Al “Carnival Time” Johnson, Frogman Henry, Wandra Rouzan, and the Dixie Cups who are slated to perform the May weekend too.

Jazz Fest has been a career-boosting venue to countless acts since the first gathering at Congo Square a mere four years after the Voting Rights Act assured African Americans of suffrage. As it grew from a roots event into an economic engine, purists bemoaned that Jazz Fest had gone short on jazz to cash in on pop culture sprawl. A sliver of truth there; but culture is business, and the festival kept a core identity with New Orleans Style. The idiom pioneered by Armstrong, Jelly, Bechet among others has vaulted into new expressions through musicians like Dr. Michael White, Gregg Stafford, Tom McDermott and Aurora Nealand, advancing new songs in the old idiom. And so it goes at the Fair Grounds stages, sounds from a cultural mosaic rich and diverse.