The 2014 New Orleans Jazz and Heritage Festival’s second Friday finished with a diva duel.

Old-school champion Chaka Khan struck first when a prerecorded sample of rapper Melle Mel saying her name introduced her hit “I Feel for You” as she began her set on the Congo Square Stage.

On the nearby Acura Stage, Christina Aguilera out-diva’ed her by waiting until shortly after 6 p.m. — more than 15 minutes late — to come onstage in a black minidress, white dress shirt and glitter houndstooth jacket that she promptly shed.

Her black fedora and hand gestures on the opening “Dirrty” evoked Michael Jackson, but she traded the hat and shirt for a tiara and boa to sing “Lady Marmalade.” Over the next 90 minutes, she ranged though covers, her own hits and a version of Led Zeppelin’s “Whole Lotta Love” that suggested she’d have been an outstanding rock singer.

Aguilera’s career began in 1999 when “Genie in a Bottle” topped the charts.

In recent years, she has been as well known for being a judge on the TV singing competition “The Voice” as for her music, though she’ll relinquish that role next season to Gwen Stefani. During her show, she nodded to fellow judge Adam Levine when she sang a verse and chorus of Maroon 5’s “Moves Like Jagger.”

“My senses are heightened,” Aguilera said, referring to the baby bump visible under her black dress. She announced two months ago that she’s pregnant with her second child, and the dress made it obvious. That didn’t slow her down, though Aguilera sat on a couch to sing Nina Simone’s “I Want A Little Sugar in My Bowl.” Later, she recalled loving the blues as a kid before singing B.B. King’s “The Thrill Is Gone.”

The set was unusual for Jazz Fest with its four dancers and numerous wardrobe changes, though the latter largely involved new hats and jackets. By arena standards, it was less of a show than fans have come to expect. By Jazz Fest standards, it was a lot.

Aguilera didn’t rely on the trappings, though, nor did she leave it to the dancers to entertain the crowd. She is a physical, committed singer, and her voice is unquestionably powerful.

Often, in fact, her voice was stronger than the songs she sang. The nod to big-band “Candyman” was pleasant, but Aguilera seemed to invest more energy and emotion than the song merited. On a number of occasions, the set seemed to be more about the display of accomplished work than real feelings.

On the other hand, fans excitedly videoed the duet with A Great Big World on the hit “Say Something.” For it, she sat down beside the piano and let the simplicity and the song do the work.

By the time she got to the concluding “Fighter,” Aguilera had established in no uncertain terms that she has the powerful voice people came to see. It just wasn’t clear what she wanted to say with it.