After an earth-shaking, string-shredding, crowd-loving, tour-de-fiddle-force rendition of "The Devil Went Down to Georgia," during a brief intermission in Zac Brown Band’s two-hour-plus show at Summerfest on Saturday night, two guys stormed past me in the concourse, and I overheard one of them grumble, "I didn’t come for this; I paid to hear country music," as they headed toward the exit.

They may have been the only ones at the American Family Insurance Amphitheater who were disappointed.

Absolutely, Zac Brown and his mesmerizingly talented seven-person band played a lot more than their country-station staples, like "Chicken Fried" and "Toes" – which they dutifully performed – and, absolutely, the crowd loved it. In his opener-less, extended set, nearly a third of the group's 30 songs were covers; and, given the audience reaction (at least among those that hadn’t left), and the way Zac Brown Band’s gifted and low-key-charismatic musicians enacted them, the pilfered pieces may have been the most popular.

Summerfest’s second headlining country superstar, following Luke Bryan’s high-energy show on Thursday, the Zac Brown Band brought a different sound and feel to the amphitheater. Less a showman than Bryan, and with lots more instrumental prestige backing him, the bearded Brown – whose guitar players were spitting images of him – is content to do more with less. For most of the performance, he stood front and center, playing his guitar and singing into his microphone, sometimes venturing to the edge of the stage to shake hands with – not high-five – front-row fans; otherwise, he just smiled and sang, and the music did the rest.

The band started with "Keep Me In Mind" and then quickly appeased the American flag-attired audience with "Toes," the 2009 vacation-themed ballad from ZBB's debut album "The Foundation." With unbeatable weather on a holiday weekend, the concert had a distinct Saturday party vibe, early on with a beach ball batted around and later, as unoccupied seats in the sold-out were steadily filled with laughing, drinking, singing and swaying fans.

Zac Brown, either out of intent or indifference, isn’t much for audience banter. After the second song, he said, "So this is the 50th year (of Summerfest)? Man, 50 years." And later, he’d chime in with, "I hope y’all feel as good as we do up here right now." He clearly knows his band’s musical ability is more than sufficient as a replacement for jokes and dropped-in Milwaukee references.

Indeed, watching a Zac Brown Band show is like seeing your favorite old generic jam band play – if your favorite old generic jam band was also phenomenally skilled and polished and cohesive and performing at a top-notch venue like the American Family Insurance Amphitheater. The eight members all clearly love playing music together, jiving and harmonizing and faux-competing with each other, lifting the whole thing from a country concert to a full-blown, fun and jubilant spectacle.

In particular, Jimmy De Martini is a sight to behold on the violin, and the band allows him to shine, shaving the strings off his fiddle and offering a bluegrass sound to the ensemble. At one point, Coy Bowles and Clay Cook, both of whom play the guitar and keyboards, had a head-to-head guitar battle, one-upping each other and eventually embracing an explosive cover of Metallica’s "Enter Sandman."

Zac Brown Band just released its latest album, "Welcome Home," in May. And while they certainly played several songs off that record – "Roots," "2 Places At 1 Time," "Family Table," "My Old Man," "Start Over," "Your Majesty" and more – this was no marketing tour event. They blended their country, southern rock, bluegrass, bluesy, folkish, jam-band and hard-rock styles, particularly seeming to relish the heavy metal opportunities.

After intermission, Brown took the mic for one of his only audience addresses, to tell people about Camp Southern Ground, which he founded as a nonprofit organization for children. For "Start Over," the whole band sat down next to one another on the steps of the stage for a singalong with the audience; "you sound great," Brown told us. Then they elated and enraptured the crowd with a high-octane, instrument-heavy version of Queen’s "Bohemian Rhapsody."

Zac Brown Band’s pulsating home stretch included a pounding cover of Guns N’ Roses’ "Paradise City" – perhaps the climax of the set, and a song also covered by Bryan two nights prior – then a few new-album originals and the guitar duel before the exhilarating "Enter Sandman." After the curtain went down, the audience roared, predictably, for the expected encore. And, sure enough, the eponymous singer came out, solo and acoustic, to perform "All The Best," and then, with his full group, the beloved hit "Chicken Fried" and a soulful "Homegrown." 

The way the crowd cheered, fans could have listened to another 10 encore songs. That is, those that hadn’t left at intermission, angry that Zac Brown Band wasn't just playing its same old stuff.

Set list

"Keep Me In Mind"
"Toes"
"Family Table"
"As She’s Walking Away"
"Let It Go"
"Baba O'Riley" (The Who cover)
"Your Majesty"
"Day For The Dead"
"Loving You Easy"
"Free"/"Into The Mystic"
"The Devil Went Down To Georgia" (Charlie Daniels cover)
"2 Places At 1 Time"
"Whipping Post" (Allman Brothers cover)
Intermission
"Colder Weather"
"Bohemian Rhapsody" (Queen cover)
"My Old Man"
"Use Somebody" (Kings of Leon cover)
"Start Over"
"Tomorrow Never Comes"
"Jump Right In"/"Castaway"
"Where The Boat Leaves From"
"Knee Deep"
"Roots"
"Paradise City" (Guns N' Roses cover)
"Whiskey’s Gone"
"Beautiful Drug"
"Enter Sandman" (Metallica cover)

Encore
"All The Best"
"Chicken Fried"
"Homegrown"