Consider it one of the challenges of superstardom.

You're not in tour mode, but you land a big gig. You don't have musicians on retainer and rehearsed. You don't have an elaborate stage set and crew to go with it. So what do you do?

If you're Usher, the biggest R&B star of this century, you call the Roots, the great hip-hop band, to play a handful of festival shows with you this year. But since they have a nightly TV gig with Jimmy Fallon, they weren't available to join Usher Thursday night at the Minnesota State Fair grandstand.

Instead, he phoned his pal, rapper Lil Jon, the master of crunk. Good move. Because when Lil Jon hit the stage after Usher's first three songs, the energy increased twentyfold.

He collaborated with Usher on "Missing U" and then threw down his own hits, 2003's "Get Low" and 2009's "Shots," elevating the party in a way that the ballad-oriented Usher couldn't. It didn't hurt that Lil Jon pandered to the 12,779 fans by wearing a Twins hoodie and cap.

Having Lil Jon on board kept Usher loose. This wasn't a tightly choreographed spectacle, like Usher has delivered in Twin Cities arenas four times, most recently in 2014. This was a low-budget (no band, just a DJ and dancers), big-ticket ($72 to $97) performance of crowd-pleasing quality.

R&B star Usher performed at the State Fair grandstand. For more photos from the show, go to startribune.com/galleries.

The Chattanooga-born, Atlanta-based Usher, 38, who came across as a Michael Jackson wannabe in his early concerts, showed off some fancy dance moves that seemed flashier because he was sporting shiny gold sneakers. However, his moves were not as vibrant as those of his six backup dancers.

Not that anybody was complaining. Because Usher flashed his magnetic smile, pulled off his shirt to show off those famous abs and played all the hits that fans wanted to hear. And he let the fans carry the vocals on several of his biggest numbers, including "Nice and Slow" and "U Got It Bad."

Usher still has a supple voice, a smooth gospel-infused R&B instrument with a sexy falsetto. After he thrilled the crowd with "Burn," Lil Jon shouted: "Make some noise for real freaking singing." Indeed.

By the same token, especially considering the ticket prices, it would be nice to have live musicians instead of a DJ providing the sounds. At least, this setup enabled Usher to keep the concert loose and spontaneous. At one point, DJ IZ stopped the show and told Usher that he skipped a song. So they pulled out "U Remind Me," the 2001 smash he recorded with Minneapolis' own Jimmy Jam and Terry Lewis.

Usher had a mission at the State Fair: "To sing for my ladies." He did that just right on "U Make Me Wanna," his 1997 breakthrough hit and one of Thursday's highlights.

Before the finale in this seemingly short 75-minute concert, Usher delivered a message about sticking together and helping people harmed by Hurricane Harvey and people who have suffered losses of loved ones. Then he sang "Without You," his 2011 collaboration with David Guetta, with more sustained spirit than anything he'd done before that.

Sometimes it's good for a superstar to have his head in the real world instead of tour mode.

Twitter: @JonBream • 612-673-1719