By Jim DeRogatis, Chicago Sun-Times

For nearly three decades, the Ex has been one of the most revered names in the rock underground. An “avant-ethno-improv-punk band” from the Netherlands, as their Chicago label Touch and Go describes the quartet, it is second only perhaps to Sonic Youth in terms of stretching the envelope and refusing to recognize any limits for what rock ‘n’ roll can and cannot do.

Given that history and adventurous aesthetic, it comes as no surprise to find the current Ex lineup of Andy Moor, G.W. Sok and Terrie and Katherina Ex collaborating on their most ambitious tour of the U.S. with Ethiopian saxophonist Getatchew Mekuria, a giant of a man adorned in a lion’s man and renowned in his country for developing ‘Shellele,’ a musical style that originated with tribal war chants.

Long before the Ex met Mekuria, the musicians had become fans of his work via a worn-out cassette they’d found for sale in a street market. The African influence has long been evident in the group’s music. “It’s there in the polyrhythms and the interlocking guitar lines and melodies, and also in the idea that everyone is playing all the time,” as Moor says. “We’re influenced by African music on lots of different levels, but we’re not trying to sound like an African band or imitate them in any way. That wouldn’t really make much sense.”

As for how the band came to meet their hero, that “started out as a sort of mad project of Terrie, the other guitar player from the Ex, because he traveled in Africa for a year, and he spent a month in Ethiopia at the end of the travel.” With a modest grant from the Dutch government, the Ex toured Africa, playing whatever gigs could be arranged: cow barns, community halls or performances in the street powered by a generator in a truck and advertised via megaphone and fliers.

“When we first decided to play there, I think Terrie and I went on ahead in January or April and said we’d like to come back the next year in January,” Moor says. “People said, ‘Oh, that’s too long away for us to organize anything; you should just show up in January with your instruments!’ And in the end, that’s actually how we did it.”

The group entitled one of its songs “Getatchew” on the 2004 album “Turn” even before it had met Mekuria. Once it did, he was invited to perform with the band during its 25th anniversary celebration in the Netherlands, and that eventually led to a 2006 album, “Moa Anbessa,” and the current tour. “He invited us, to be honest,” Moor says. “It was more his idea to do this record and then the tour.”

Sometimes described as an “anarchist” group, perhaps incorrectly, Moor laughs when asked if it isn’t ironic for a project so rooted in spontaneity to have celebrated a 25th anniversary, much less the approaching 30th. “I think of that all the time,” he says. “Every year I wonder what I’m gonna do next year with the Ex, but we kind of imagine that we can continue doing this for the rest of our lives, because we’ve come this far, and why would we suddenly lose the spirit? If that happens, we should stop; we’re not continuing to do it just because that’s what we do.

“We genuinely look forward to it each year, and we constantly redefine what we’re doing: Every time we rehearse again, we throw out all the old songs and start again, and by doing that, you feel a bit like you’re a new band each time you start, even though it’s the same musicians, because we’re not relying on all these old songs. That keeps it really fresh, though it’s a bit tough for the audience sometimes, because they never get to sing along. Each time they get to know the CDs, we’re not playing them anymore. But for us it’s really vital and necessary. I just think songs have a kind of life in them, a certain amount of battery power, and then once the battery runs out, you have to leave them alone.”

One way the musicians stay fresh is through collaborating with other players: Katherina Ex recently linked up with Chicagoan Jon Langford of the Mekons and the Waco Brothers to record the self-titled debut by their KATJONBAND, to be released on the local Carrot Top label next month, to name one of many side projects. “You might think that draws energy away from the band, but it doesn’t,” Moor says. “I get other ideas from other musicians, and I can always bring that back to the Ex. That is what keeps us creative.”

More than any particular politics, the rebel spirit lives in the Ex in terms of how its members define success both personally and artistically.

“The first definition we have of success is that we feel we can make great music at a concert; we don’t think about CDs,” Moor says. “We go into this practice room to rehearse, and the biggest goal that we have is to make a great live set. Even though you made the songs yourself, you have to learn how to play them, and that takes half a year. To me, that’s the biggest success. And then the fact that we live from that, that’s f—cking unbelievable; it’s really a gift.

“A lot of bands measure their success by they always have to get bigger and bigger. We don’t really feel like we need to get bigger: Our audience has pretty much stayed the same for 29 years, and it’s enough for us to survive. It’s a little bit difficult sometimes–we live a bit on the edge–but it’s enough. This thing we’re doing with Getatchew is one of the biggest things we’ve done. And that’s alright, but next year, we’ll be back playing in small clubs in Germany or France. We’ll be on to doing a new project, and that will be fine, too.”

Moor sums up the ambitions of the Ex by quoting Chicago critic, musician and champion of art and free jazz John Corbett. “”He described it really well: He said we win our audiences one member at a time. We’re not trying to do a Chumbawumba-style big hit where you subvert from within; we’re not even trying to subvert. We have our own musical vision, and it doesn’t seem to be connected to the mainstream. It’s our own personal vision, and we want to share it with people, and also shake it up–to send that energy. Some people will take it and do something with it, and some people won’t.

“But it does feel good when you go do a gig, and two years later you come back, and one guy says, ‘After I saw your gig, I started a band’ or ‘I did this’ or ‘I left my job.’ Of course, we didn’t prompt that change. We were just a sort of catalyst that set it going.”

The Ex and Getatchew Mekuria
8 p.m. Sunday
Logan Square Auditorium, 2539 N. Kedzie, Chicago
$15
www.emptybottle.com

AND

12:15 p.m. Monday
Pritzker Pavilion, Millennium Park, Chicago
Free
(312) 742-1168