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When British post-punk band the Pop Group reunited after more than 30 years, its members had a rule. This was not going to be just a nostalgia trip and would have to include new material. But according to singer Mark Stewart, they also went back to more primal sources for the recent disc, “Citizen Zombie” (Freak 9).

“This new song, ‘Shadow Child,’ is like when me and my brother were 3 years old,” Stewart said over the phone from London. “We’d lie on our backs and go into these manic, hyper, mental things just to get the blood going.”

The Pop Group’s approach may be elemental, but it’s hardly simple. The band disassembled familiar song structures and embraced dissonance, free improvisation, funk and disco beats as well as Jamaican dub techniques — sometimes all of them simultaneously.

Stewart’s lyrics decried British society under Prime Minister Margaret Thatcher or offered abstract love songs. While the group did not amass a huge following, it inspired numerous prominent artists, not all of whom are musicians.

While the Pop Group has become globally influential, Stewart found his catalysts within his hometown of Bristol, England.

“Bristol is a small enough town that everybody mixes,” Stewart said. “From an early age, I was going to West Indian clubs to listen to the sound systems. And I used to walk home from school and trawl junk shops where they’d have (beat poet) Gregory Corso books and weird funk records, which was the route into jazz.”

Meanwhile, the Clash showed a route to becoming a musician.

“The fierceness and energy of punk knocked down the doors and enabled normal kids to buy guitars in these cheap shops,” Stewart said. “Before that, it was prog rock and the idea of being a musician was a long way away. And with post-punk, the rules had been torn up.”

Ignoring rock conventions, the Pop Group inverted instrumentalists’ typical roles on its 1979 debut album, “Y,” and keep doing so on “Citizen Zombie.”

Guitarist Gareth Sager’s solos can be fragmented, linear or his own combination of both. Drummer Bruce Smith defied punk’s aggression to include multiple dance beats, and sometimes everyone would drop out except for bassist Dan Catsis.

“We were constantly going out dancing,” Stewart said. “We learned from funk and dub to take everything away. At these sound systems, the bass would completely overload. And being next to the bass is like being in the womb.”

Stewart adds that the Pop Group intended to question structures and hierarchies in its music, as well as its lyrics. He connects the polemical “For How Much Longer Do We Tolerate Mass Murder?” and “We Are All Prostitutes” to his romantic, if oblique, “She Is Beyond Good And Evil.”

“For me, the concept of love is a political thing,” Stewart said. “If you love humanity, you desire change.”

After the Pop Group disbanded in the early 1980s, other Bristol musicians, such as Portishead, turned their predecessor’s take on spacious dub into a slower genre, trip-hop. In the United States, St. Vincent covered “She Is Beyond Good And Evil” on “Late Night With Jimmy Fallon” four years ago.

Another fan, “The Simpsons” co-creator Matt Groening, asked the Pop Group to reunite when he guest-curated England’s 2010 All Tomorrow’s Parties Festival.

Although it took another year for the reunion to actually happen, Stewart is excited to bring the Pop Group to the Levitation Chicago festival on Friday, which will be the band’s local debut. It’s also recently reissued a 1980 album, “We Are Time” (Freaks R Us), and Stewart finally came up with a term to describe its music.

“It’s that weird, boyish thing of giggling and pushing into each other and taking control of the rhythm,” Stewart said. “It’s quite hooligan, in a way. It’s hooligan jazz.”

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When: 11:30 p.m. Friday

Where: Thalia Hall, 1807 S. Allport St.

Tickets: $25-$35 (17+); 312-526-3851 or thaliahallchicago.com