Underneath the sculpture of Professor Longhair that hangs atop the Acura Stage at Jazz Fest was, very appropriately, a grand piano. And in the true spirit of the legendary New Orleans piano innovator, it was played all day long Saturday.

Saturday at the New Orleans Jazz and Heritage Festival presented by Shell was a piano bonanza, starting with Texas boogie-woogie piano star Marcia Ball, followed by a tribute to Fats Domino. Headlining the day was Elton John, who attracted the biggest crowd of the festival to date this year, with crowds stretching across the Fair Grounds and into the surrounding racetrack.

John’s set stretched just over two hours, but even that didn’t seem enough time to pack in his decades of hits.

The first hour alone was enough for a dozen careers: “Levon,” “Tiny Dancer,” “Bennie and the Jets,” “Candle in the Wind” and “Love Lies Bleeding,” a suite that built with drama. But then came the second hour, when he moved forward in time, with “Hey Ahab,” a song from a recent collaboration with Leon Russell, “That’s Why They Call It the Blues,” “Sad Songs (Say So Much)” and more.

His five-member band, all in black suits, played dutifully, but it was their boss who added jazz fills, with special Longhair-like arpeggios injected into the music. As the set wore on, John became more enamored with popping up from his bench to thank the crowd.

Early in his set he said it was an “honor” to play following Jerry Lee Lewis, whom he called “my hero.”

“One of the reasons I wanted to play piano was because he kicked it, he stood on it, he abused it,” John said.

A Louisiana native son, Lewis, at 79, should not be expected to be as animated as John remembers him. He stood at his piano rigidly, letting only his fingers get wild. He combed two fingers up and down the registers, banged keys like a jackhammer, yelped, purred and answered many songs with the only refrain that felt appropriate: “Mercy.”

Dressed in a white jacket, tie and shoes, Lewis played a set of songs, primarily from his Sun Records period, that represent a significant portion of rock ’n’ roll’s blueprint. The crowd knew them all: “Roll Over Beethoven,” “CC Rider,” “Whole Lotta Shakin’ Going On,” “Great Balls of Fire” and more. Frequently, he rested his arms and let the band play on until raising his left hand and letting it drop into the dance, followed by the right that added flavor.

He was there to be seen, but the music was no museum piece. Each person among the thousands knew every word and, as he said after “Whole Lotta”: “That one brings back a few memories.”

Saturday provided a special opportunity for festivalgoers in the know to check out some of city’s best musicians all on one stage. They’re called the Midnite Disturbers, and every year, this supergroup plays a set of electrifying New Orleans funk.

Ten horn players — including “Big Sam” Williams, Trombone Shorty, Corey Henry, Galactic’s Ben Ellman and lead Disturber Shamarr Allen — lined the stage, where they syncopated riffs, traded solos and taught the crowd to take a cue from the Lil’ Rascals Brass Band and “buck it like a horse.” Each song split into thirds, with the trombones, trumpets and saxophones engaged in duels.

Helming the center was Galactic drummer Stanton Moore, who traded his kit back and forth with drummer Kevin O’Day, as well as percussionist Mike Dillon.

Musically, this was a set that would have delivered on either of the main stages, but within the small confines of the Jazz and Heritage Stage, it became a house party. Allen and O’Day freestyled at the end, but by then, they were just showing off for fun. This was organized chaos that never let up.

Earlier, at the Blues Tent, the bill was titled “New Orleans Classic Divas,” but the set belonged to just one of them: Wanda Rouzan.

Rouzan performed solo for the majority of the hourlong set, backed by a big band featuring three horn players who helped beef up her set list of oldies from the heyday of New Orleans R&B: “Ooh Poo Pah Doo” (Jessie Hill), “I Know (You Don’t Love Me No More)” (Barbara George), “Let the Good Times Roll” (Shirley and Lee) and even the “Electric Boogie” that served as an instructional for a group electric slide lesson.

Rouzan’s roots go back to her time in the Rouzan Sisters, a sister act that had one hit single, “Men of War,” in 1964. Dedicated to local men shipped to Vietnam, the song appeared late in the set. Starting with a rendition of Taps, it proved to still have relevance today.

Up to that point, Rouzan led a rousing dance party with revelers crammed together in every aisle and entryway. Despite the suggestion that the fire marshal was likely worried by the human traffic jam, it was too late: Rouzan had already fired up the crowd. “I want you to act like you’re in my living room in my house and we’re having a party,” she said.

She sang with bawdy luster and commanded the crowd with wisecracks and, indeed, diva swagger. Hips were swiveled, and she got to high stepping before teaching the crowd to do the electric slide. They complied. When she broke out a whistle, it was time to go to “Treme” with John Boutte’s theme from the television show. At that point, a second-line formed in the crowd, and there was no going back.