Every Christmas for 18 years, the internationally famed jazz band the Bad Plus — with Reid Anderson on bass, Ethan Iverson on piano, Dave King on drums — has played Minnesota's Dakota Jazz Club.

"Dave called me in 2000 and said he had two friends coming into town for the holidays to record some stuff," Dakota owner Lowell Pickett recalled. "He wanted to know if they could play a couple of nights."

Lowell advertised the late December concert as "Dave King and Friends" with a $5 cover. "Dave saw the ad and called me and said, 'Can we change that to the Bad Plus?' Who was the Bad Plus? Nobody knew, so I changed it to 'The Bad Plus Featuring Dave King and Friends.' "

Fast-forward 18 years. Since that first Dakota date, the Bad Plus has released 13 albums and performed thousands of shows. Yes, thousands. "It's been, like, 150 shows a year since 2003, and 2002 had at least 30 or 40, and 2001 had about 20," King said this month, just back from a 12-day, 12-city run through Europe. "That's far more concerts than any working jazz group in history."

Along the way, Anderson, Iverson and King broadened the definition of jazz, redefined the piano trio and created a significant body of original music.

And if you want to catch the original trio, this week is your last chance, unless you happen to be visiting New York next week. On Jan. 1, Iverson will step out of the band and Philadelphia-based pianist Orrin Evans will step in. Between now and then, the Bad Plus version 1.0 will play four nights at the Dakota and a week at the Village Vanguard.

Bursting with ideas

Anderson and King grew up in Golden Valley and have known each other since junior high. Anderson met Iverson at the University of Wisconsin-Eau Claire, when Iverson was still in high school in Menomonie, Wis. They all went to shows at the Dakota and the Walker in the 1980s, young musicians hip to McCoy Tyner and Bill Frisell.

Sometime in 1990, Anderson recalled, "we got together once in my parents' living room. That was an unremarkable meeting. We were just young kids trying to push ourselves and push the boundaries, but without the skills or perspective to do it very successfully."

They went their separate ways but kept in touch. They pursued their own musical paths and played on each other's early albums. "One thing led to another," Anderson said, "and we thought — we know each other. Let's try to play together every couple of months and commit to that and make a record."

By their 2000 Dakota show, they were all seasoned musicians. They committed to being a leaderless band, to playing collective group music, to developing a sound and to staying together.

Their eponymous debut album, recorded in Minneapolis and released on the Spanish label Fresh Sound New Talent, made New York Times jazz critic Ben Ratliff's Top 10 list for 2001. "When a band starts life at this level," Ratliff wrote, "there's great hope ahead."

Their third album, "These Are the Vistas," came out on Columbia in 2003. It was greeted with cheers and howls. "People got upset about it," Iverson recalled. "That was a clear indication that we must be having an impact with our music, that it could create that kind of discourse." The Bad Plus was called a one-joke movie and the Great White Hype. (One reviewer dismissed their music as "disgusting tunes of pure madness.") For a time, this was high drama in the jazz world.

From the start, the Bad Plus stood out. They were bursting with energy and new ideas, and they could be very loud. Everything they did was unexpected. They played their own original music (all three are composers) and covered pop and rock tunes as if they had written those, too.

One of the tracks on "Vistas" is a fierce and cheeky cover of Nirvana's "Smells Like Teen Spirit" that swerves into improvisation and ends in thunder. To this day, it's the song the band is best known for, despite dozens more that exemplify the band's breadth and depth. They can play Black Sabbath, Stravinsky's "The Rite of Spring," their own music or someone else's and still sound completely like themselves.

End of an era

Announced in May on the band's Facebook page, the news that Iverson would be leaving came as a shock to many fans. Anderson, Iverson and King are road warriors of a special kind. While they have occasionally performed and recorded with guest artists — singer Wendy Lewis, saxophonist Joshua Redman, guitarist Frisell — the band has never had a lineup change or even a sub.

Leaving the band was Iverson's idea. "I felt personally too uncomfortable, and also felt like the statement had been made," he said.

When asked if Iverson's decision was surprising, Anderson said no. King described growing frustration between Anderson and Iverson, "a smoldering kind of distrust."

Iverson's interests were increasingly outside the Bad Plus, including performances and recordings with other musicians and the jazz criticism he writes for his blog "Do the Math," which made the other two band members uneasy.

This is an emotional time for all three, but they have always been pros, and reviews of their farewell tour have been glowing. "The Bad Plus is ending its first long chapter on a spectacular high," longtime jazz critic Andrew Gilbert wrote in the San Francisco Classical Voice.

King put it this way: "Every time we play, everybody's throwing down."

Iverson has many projects going. He's working on a piano concerto and wants to form a new band (but not a piano trio). He's writing for the New Yorker magazine and eyeing a book.

Anderson, King and new pianist Orrin Evans will continue as the Bad Plus. "We didn't have any auditions or anything like that," Reid said. "We just said let's call Orrin and see if he's open to doing this. He said yes immediately." They've recorded an album, "Never Stop II," for release in early 2018, and have bookings well into next year.

The end of an era invites reflection. The band members were willing to offer some thoughts. So were Pickett and Philip Bither, the Walker's performing arts curator. Bither brought the Bad Plus to the Walker several times, most recently in September for a concert with Frisell.

Reid Anderson on playing the Dakota for 18 years straight: "It's been very meaningful for us to feel the support of our hometown. That people have come back year after year, and the audience has grown, has been like a localized symbol of what we set out to do — to be a band, to create a sound and to have actual fans in the world. It's all we could really ask for."

Ethan Iverson on the band's success: "I never expected to have a career in this music that was notable. My whole life, I assumed I'd just be on the fringe, because a lot of my great jazz heroes were and are on the fringe. So to have had this amount of exposure really shocked me. … I regarded haters as more or less an honor. Having haters means you're doing something."

Dave King on the Bad Plus' impact on jazz: "If I look back on the last 18 years, I think the Bad Plus challenged the piano trio. We challenged it by being leaderless. We challenged it by having three composers. We challenged the dynamics of the piano trio, and the oeuvre of the piano trio. … We took every classic format of the piano, bass and drums and we turned it upside-down."

Lowell Pickett on the band's overall impact: "The Bad Plus helped people understand what improvised music can be, and another way that it could grow. … They've proven over the years that their creativity and their virtuosity were the real deal. They're just such incredible musicians, and they write so beautifully. All three of them."

Philip Bither on their contributions to jazz: "I've been following them ever since I heard 'These Are the Vistas.' There was this big critical split, with some of the jazz critical community dismissing them as a novelty. … I felt like those first records were great and what jazz needed, in a certain way. … They've proven a lot of skeptics wrong with the seriousness of their original compositions. … I think they have contributed a lot to helping shape the jazz of our time."

Pamela Espeland is the Artscape columnist at MinnPost and blogs at bebopified.com.