The Zac Brown Band brought along a huge Ferris wheel, a lot of great food and some country music icons for the Southern Ground Music & Food Festival as fans invaded Nashville's Riverfront Park on Friday and Saturday (Sept. 27-28).

Kenny Chesney, Kenny Rogers and John Fogerty were among those making guest appearances during the ZBB's nightly "super jam." And Willie Nelson mesmerized the crowd with an extended set despite a shoulder injury that sidelined him earlier in the week.

Nelson kept his Family band on its toes throughout his Saturday afternoon performance as his vocal and guitar phrasing jumped ahead even more unexpectedly than usual. Of course, one of the joys of watching Nelson is seeing how far he pushes his music to the edge before pulling it back into his pocket. It's what he's always done in his concerts, and it's a quality that keeps even his old songs fresh after all these years.

A shoulder injury forced Nelson to reschedule several concerts last week. Even the Nashville date had been canceled, but Nelson later announced he would play the gig with a guest appearance by Gov't Mule guitarist Warren Haynes.

A variety of other acts, including the Eli Young Band, Kacey Musgraves, Blackberry Smoke, Edward Sharpe & the Magnetic Zeros and Dawes performed during the two-day festival, yet the main attraction was clearly the Zac Brown Band. The hits were played during their headlining sets, but the promise of some interesting musical turns added even more excitement.

With little fanfare, Brown and his band began singing the opening line of the First Edition's "Just Dropped In (To See What Condition My Condition Was In)" as Rogers strolled onstage to sing the song that became his first major hit in 1968. Rogers and Brown later swapped verses on "The Gambler."

Chesney's stint onstage included a performance of the ZBB's "Knee Deep" and Tom Petty's "Runnin' Down a Dream" while Jason Mraz delivered one of his biggest hits, "I'm Yours." The Friday night offering also included a surprise guest appearance by singer-songwriter Amos Lee, who joined the band for "The Day That I Die," reprising their collaboration from the ZBB's Uncaged album.

The Stellas featuring Lennon and Maisy made guest appearances both nights, and Musgraves sat in with the band Saturday to perform her new single, "Follow Your Arrow." Clare Bowen, star of ABC's Nashville, also joined Brown for a duet on Van Morrison's "Into the Mystic."

Big guitar riffs rule at festivals, and nobody has more of them than Fogerty, who grabbed his guitar toward the close of the show Saturday to kick off the opening chords of Creedence Clearwater Revival's "Bad Moon Rising." He quickly followed it up CCR's "Lookin' Out My Back Door" and his solo hit "Centerfield."

In addition to "Into the Mystic," Brown's sets included a few acknowledgements of the band's eclectic influences that ranged from expected standards such as the Charlie Daniels Band's "The Devil Went Down to Georgia" to instrumental snippets of Led Zeppelin's "Kashmir" and Edgar Winter's "Frankenstein." The Stellas' Saturday appearance included a cover of TLC's "Waterfalls," and one of the more interesting moments both nights was when Brown and his bandmates grabbed bongos, a djembe, a cajon and other percussion instruments to perform a somewhat obscure James Taylor song, "The Frozen Man."