Jason Isbell

Guitarist Jason Isbell had parted ways with the Drive-By Truckers when the Americana rock band played the Jazz and Heritage Festival in 2008. But on Friday, Isbell was well received at his debut at the Fair Grounds, dressed all in black as he played songs ranging from his days in the Truckers to last year’s excellent “Southeastern.”

That album presented a recently sober Isbell writing and singing with newfound clarity, and his set had a similar focus. He occasionally showed his guitar prowess, but his set was about songs such as “Flying Over Water” with the lines as fine as “From the sky the highway’s straight as it can be / a string pulled tight from here to Tennessee.”

Unfortunately, many of the songs on “Southeastern” are mid-tempo, acoustic and earnestly plain-spoken. At some point, the audience was ready for a change, and Isbell picked it up at the end with a raw version of “Never Gonna Change” from his Drive-By Truckers days, and the fun boogie of “Super 8” and the hope, “I don’t want to die in a Super 8 Motel.”

The set marked Isbell as a work in progress, but it’s hard to imagine that many more personal and honest sets were played at the Fair Grounds on Friday.

Public Enemy

Last year, rap group Public Enemy was inducted into the Rock and Roll Hall of Fame, but Friday on the Congo Square Stage, original members Chuck D, Flavor Flav and Professor Griff showed they’re not a nostalgia act.

The set leaned heavily on the group’s classics, but the sound was augmented by a live band and DJ Lord. The energy came from the beats, aggressive samples that remain confrontational, and Chuck D’s stun gun of a voice.

Because Jazz Fest prides itself on being a family festival, Chuck D and Flavor Flav had to watch their language. That led to some unintentionally comic moments as they used initials or sounds where they normally would swear.

“---- the game if it don’t mean nothing,” Chuck D said, criticizing the radio and celebrating hometown heroes Allen Toussaint and Fats Domino among others.

Flavor Flav remains a wild card. He brought Chuck D’s mom onstage to wish her a happy birthday, and he dedicated “31 Flavors” to his lawyer, “who helps me with my cases.”

Being in New Orleans clearly meant a lot to Chuck D, who dedicated “Timebomb” to The Meters and declared the city “the home of all music.” As uneasy as he seemed with modern technology, he announced his Twitter handle before the set’s end.

By the time Flavor Flav took “Fight the Power” into the crowd, Public Enemy had reinvented classics, done push-ups, quoted Led Zeppelin’s “Kashmir” and showed the sort of vitality we want from any band, much less a 25-year-old one.

Rotary Downs

New Orleans indie rock band Rotary Downs used their set on the Samsung Galaxy Stage at the New Orleans Jazz and Heritage Festival to debut new songs from “Traces,” their fifth album, released Friday.

The emphasis on “Traces” didn’t seem to affect their reception, and it animated the band. Singer James Marler’s a cool onstage presence, but bassist Jason Rhein and guitarist Alex Smith bounced with excitement at times.

Despite the band’s three-guitar attack, Rotary Downs sounded surprisingly light. Instead of adding sonic heft, the guitars contributed subtleties — fragments of melody that sweetened the songs.

A cover of Gary Numan’s “Cars” energized the crowd and underlined a point the rest of the set made — that their psychedelic songs are naturally nocturnal. But Rotary Downs made them work early in the afternoon.