For 20 years, the Klezmatics have operated under one rule: there are no rules.

“I think our basic technique is to make a plan and be really open and receptive when something exactly the opposite and unexpected happens,” says Frank London, trumpeter and keyboardist for the Grammy-winning, New York-based klezmer band. “You’ve gotta have a plan that you can ignore.”

That idea — of being constantly open to suggestion and free to reverse course at a moment’s notice — has kept the sextet together despite numerous personnel changes and seismic shifts in musical direction. The band specializes in traditional klezmer music, but incorporates elements of pop, folk, classical, world beat and even African-American gospel music into their sound.

“I would say the way we’ve changed over the last 20 years — especially in the last 10 years — is that we’ve really, really become our own group,” London says. “We’re not just a klezmer band anymore. We are the Klezmatics. We have a sound.”

In the beginning, the group worked hard at faithfully reproducing the klezmer sound handed down from Eastern Europe and early 20th century New York. But with album titles like Rhythm & Jews and Jews with Horns, it was impossible to ignore the fact that the band was operating with an almost punk-rock attitude.

“Absolutely,” London agrees. “When we did Rhythm & Jews, it was more or less the first time that anyone had thrown the word ‘Jew’ on the cover of a record. Especially not as a pejorative,” he adds with a laugh.

“There’s a whole Lenny Bruce routine about ‘Jew-ish.’ You know, ‘You’re not a Jew, you’re Jew-ish,’ right? We just said, ‘Yeah.’ It was definitely a moment of group self-pride, even though I should add that not everyone in the band is a Jew. But as a group, we play this Jewish music and we’re proud of our identity.”

Occasionally the Klezmatics run afoul of klezmer purists who don’t like to see the band expand the genre’s boundaries. London says that he understands that point of view, but doesn’t agree.

“If someone says to me that a tradition should never change and that’s the definition of a purist, then that’s actually an erroneous assumption. Because they’re trying to fix a certain moment in an evolution and say, ‘This is the moment I like, therefore I will call this the authentic moment.’ But traditions live and breathe and grow and transform.”

Among the Klezmatics’ cross-cultural collaborations is its 2004 album, Brother Moses Smote the Water, with African-American Jew Joshua Nelson. It addresses themes of Passover, slavery, socialism and human rights and includes “Old Testament”-based Christian gospel tunes “Oh Mary Don’t You Weep” and “Didn’t It Rain.”

The album, which was recorded live in Germany, was given a revival of sorts last year with a European tour. “So we’re touring with five other bands, the Hallelujah Baptist Revival Choir and these different gospel groups,” London says. “We were the only Jewish and white group on the tour, playing for this white European audience that’s basically there to hear black American gospel music. But then they hear the Klezmatics, doing this gospel-klezmer mix, and I just loved it. I feel at home like that.”

London also found comfort — and much excitement — when the band was invited by Nora Guthire, daughter of the late, legendary folksinger Woody Guthrie, to dive into a treasure trove of her father’s unfinished lyrics to see if the group could come up with some songs.

The effort yielded two albums, the Grammy-winning Wonder Wheel and Woody Guthrie’s Happy Joyous Hanukkah. But the project may have been jumpstarted by an offbeat introduction.

“We had just played with Itzhak Perlman at Tanglewood, which is near where Arlo Guthrie lives,” London recalls. We had played a song that was in our repertoire, called ‘Fisherlid,’ which was written by Nora’s grandmother, Aliza Greenblatt. When Itzhak walked backstage, we introduced them to each other and we’re like, ‘This is Nora Guthie, Aliza Greenblatt’s granddaughter.’

“Nora was so taken with this. She’s like, ‘All my life, I’ve been either Woody’s daughter or Arlo’s sister. I’ve never been introduced as Aliza Greenblatt’s granddaughter.’ She realized that in some worlds, that’s the defining moment.

“She told us the whole story about the lyrics. I don’t know if she’d come there with this in mind, but she told us she’d like us to work with the lyrics and it’s been a blessing. We’d have done it no matter what, but the fact of his social and political activism, mixed with his joy of life and celebration, and his punk attitude of not holding anything back, it all worked together so beautifully.”

The Klezmatics current tour as well as a recent retrospective album, Tuml = Lebn, plus a forthcoming concert DVD and documentary film are all part of the band’s 20th anniversary celebration. Members are enjoying the celebration of their accomplishments, London says, but they’re not inclined to spend too much time revisiting the past.

“Once all of that material is released, I think at that point we’ll say, ‘That’s enough looking back’ and we’ll move forward again.”

The Klezmatics

When: 7:30 p.m. Tuesday, March 24

Where: Congregation B’nai Amoona, 324 S. Mason Road

How much: $18

More info: 314-576-9990 x126