 -- On the eve of Hillary Clinton’s star-studded concert in Des Moines, Iowa, featuring mega-A-lister Katy Perry, the Bernie Sanders campaign held a concert of its own.

Two hours away in Davenport, Iowa, a group of about a dozen "working class" performers from around the country performed for a packed house of about 2,400 people at the historic Alder Theater Friday night. The campaign said the timing of the two competing concerts was a coincidence. As one of the organizers, Scott Goodstein put it: “There is a long lineage of progressive, working class musicians” and their show was all about that tradition.

“You can’t separate politics and music. I can’t,” singer-songwriter Wayne Kramer told ABC News. “Everything that we do is political.”

Kramer, who is best known for the 1970s band Motor City 5, pulled no punches when asked about the difference between the two concerts. “One is a manufactured, celebrity-driven, show business and the other is the real rock,” he said. “Tonight - this isn’t a question of celebrity, it is a question of sincerity.”

The bands played mostly classic rock with some folk and good old protest tunes mixed in. Singer Jill Sobule, who wrote the hit songs “I Kissed a Girl” and “Supermodel” from the Clueless soundtrack kicked off the night with a song about immigration.

“When they say they want their America back,” she sang, picking a mandolin. “What the fudge to they mean?” With a wink and smile she urged the audience to sing the chorus with the more profane version of the line. They did.

Sobule traveled from Los Angeles to join the concert, and warming up in her grey Chuck Taylors and blue velvet newsboy hat, she told ABC News that she likes Sanders because he is bringing the issues she cares about to the national stage. “I don’t think Hillary would have called herself a progressive if Bernie wasn’t in,” she said.

The second time Sobule came onstage to perform, she sang a song she said applied especially to Sanders called, ‘Underdog Victorious.’

“Wouldn't you rather have something a little loose, with a good vibe, than something too rehearsed,” she continued about their concert.

The musicians only rehearsed together once, about two hours before the show, and there were some fumbles. William DuVall, the current frontman of '90s grunge stars Alice in Chains, had an acoustic guitar that would not connect to the speakers. He switched to an extra electric guitar sitting onstage, saying it was “a sign we need some electricity.”

“I have had to listen to a lot of mean-spirited talk," DuVall said during a bridge in his song. "When people say they want their country back, they really mean they want to go backwards...But I don’t want to go backwards.

"And that’s part of the reason I am here tonight. I am ‘Feeling the Bern,'" he continued.

Last month Sanders released the names of more than 120 artists who were endorsing his candidacy. According to Kramer and Sobule, the purpose of Friday's concert was two-fold: to give a little “umph” to the volunteers knocking on doors for their candidate in Iowa and to demonstrate support for the Sanders campaign from the artistic community.

“These are great, vital artists who have come together,” he said. “There are a lot of people who believe [Sanders] is on the right track.”

The night ended with the real rockstar the crowd had waited for -- Bernie Sanders himself. The Vermont Senator came onstage and asked the standing fans, “How would you like to make history?

“Because that’s what we’re going to do… We’re going to have a grassroots movement that takes on and defeats the political and economic establishment of this country,” he said.