(CNN) — Concerts by Phish, the beloved Vermont jam band, have become known among fans as unique, once-in-a-lifetime events filled with striking visuals and spontaneous sonic explorations.

Over the decades the band has performed more than 2,000 shows and are famous for never repeating setlists — drawing deeply from their extensive canon of more than 300 original songs plus countless covers.

That hasn’t changed. But now, 41 years into their journey, the band has conceived yet another new way to experience their music live: four concerts at Sphere, the $2.3 billion venue in Las Vegas that was christened last fall with a series of shows by U2. The Phish shows kicked off Thursday and run through Sunday night.

“It’s a paradigm shift in live music and visual (presentation),” Trey Anastasio, Phish’s bandleader and creative force, told CNN in an interview last week about the Sphere dates. “It’s … an exciting new canvas.”

Phish is just the second band to play Sphere, after U2. The state-of-the-art, spherical venue is dominated by a giant LED screen some 250 feet high that wraps above and around the audience. That vast screen, along with 167,000 speakers that ensure pristine sound, make for an immersive concertgoing experience.

But while U2 played mostly the same set list and paired songs with pre-made videos that repeated each night, Phish is taking their usual freewheeling approach.

The band is not repeating any songs over their four-night run, and each show’s visuals are different and even improvised in the moment, similar to what fans have become accustomed to from Phish’s long-time lighting designer, Chris “CK5” Kuroda.

“All of our visuals can be executed, modified, and manipulated in real time,” the band’s creative director for the shows at Sphere, Abigail Rosen Holmes, told CNN. “They will follow the band’s musical performance, rather than being locked in, allowing Phish to play as freely as they would at any other show.”

Sure enough, on Thursday’s opening night the psychedelic animations and graphics appeared to soar and glide to the music, creating 3D effects on Sphere’s huge screen. Each song featured distinct visual eye candy, from layered abstract tapestries to breathtaking scenic imagery — both earthly and otherworldly.

Daniel Jean of Moment Factory, the Montreal-based multimedia studio that co-produced the visuals, told CNN that working on Sphere’s immersive’s screen “has opened the door to creativity in ways we haven’t been able to explore before. The emotions of the music, mixed cohesively with the visuals on the screen, create an emphatic moment only truly felt by those in the venue.”

Members of Phish say they studied U2’s 40-concert Sphere residency to prepare for playing the venue. Phish’s audio engineer even re-created a miniature version of Sphere’s production setup at a practice studio in Pennsylvania last summer so the band could fine-tune the shows’ look and sound.

Last week, Anastasio said it would be a challenge to use Sphere’s massive space in a way that still felt organic.

“When you see a large-scale production — you know, Beyoncé or U2 or anything that’s really a big, major pop act — the production and the music are on a click. So it makes it easier to have everything happen at the proper time,” he said. “And we don’t do that.”

But after Thursday night’s show he sounded pleased with the venue, saying he felt “an intimacy” at Sphere despite its cavernous size.

“I could see the audience so clearly, which has such a huge effect on the music. When I can look directly at people dancing, I play so much better. I can react to their energy. I did not expect that,” he told CNN via email. “It’s a huge blessing. It felt very comfortable.”

From the start Phish cultivated a profound bond with its audience

Phish’s signature sound centers around progressive rock arrangements infused with a variety of musical genres, including jazz, funk and blues and beyond.

The band formed in 1983 while its members were attending college in Vermont, where Anastasio met drummer Jon Fishman and bassist Mike Gordon. Keyboardist Page McConnell joined the group about two years later.

“We started out as a group of friends, in a room with our friends,” Anastasio said. “We would play until 1:30 in the morning, and then we would all go out to Howard Johnson’s for eggs and French toast.  Literally, like the band and the audience. And in some respects, that never changed. It still feels like that.”

In their infancy the band started playing residencies at Nectars, then a Burlington restaurant and bar with a small stage in the corner. From the beginning they practiced their complex arrangements religiously, often following Anastasio’s daily schedule detailing which times they would flesh out specific sections of each tune.

Gradually Phish built a fan base, mostly through relentless touring across the US.

“We built up this following just by playing,” Gordon says in “Bittersweet Motel,” director Todd Phillips’ 2000 documentary about the band. “It was never really records or radio or videos or anything like that that boosted our career. It was all this word-of-mouth thing.”

The fans come to shows “because they don’t know what’s going to happen,” Gordon added, “just like we don’t know what’s going to happen” — a sentiment that both band members and fans say hasn’t changed.

“We were never really in the public eye,” Anastasio told CNN last week.  “We don’t have hits, or go the Grammys, or anything like that. It’s a community, is what it is. And it really, truly is. And it still feels that way. I think that’s pretty much a big part of what makes us different.”

Anastasio says he can feel the “energy” from the crowd during each show, and that informs his decisions on what the band plays in real time — an approach Phish has taken its entire existence.

“It has a mind of its own. Everything’s fair game,” Anastasio said. “It’s like a combination of discipline and complete abandon. I don’t think you can have one without the other.”

The band’s concerts have included covers of other groups’ classic albums — and donuts

Anastasio says he enjoys spearheading the complicated logistics required to pull off their elaborate productions. His focus is making sure his bandmates stay in the moment on stage.

“If Mike Gordon is totally not thinking, he plays the sickest bass of anybody who has ever lived,” he said. “As soon as you get him thinking, he’s not playing well anymore.”

Anastasio says his most exhilarating live moments are when the band goes “completely off the map” into uncharted musical territory.

“And there are many of them … where I don’t know where the downbeat is, and I don’t know what key we’re in anymore. And my head is exploding about what Mike is playing or what Fish is playing or what Page is playing,” he said. “And … it feels like being in a tiny, tiny rowboat in the middle of a storm in the ocean.”

The band has played more concerts at New York’s fabled Madison Square Garden than any act except Billy Joel. On New Year’s Eve in 2022, Phish turned the arena into a giant undersea visual spectacle, complete with flying dolphins. A year later they created an almost fully realized Broadway show at MSG from their beloved “Gamehendge” suite, a fantasy rock opera last played in its entirety in 1994.

“People will ask us … a normal band would build something like that and then take it on tour for four years. Why do you just do these things once?” Anastasio said. “And my response would be that most of the people in the room have been seeing us for so long, we feel like we owe them a new, fresh experience.”

The band also has become well known for staging elaborate events. For Halloween, they sometimes adopt “musical costumes” and perform other artists’ classic albums, a tradition they started in 1994 with a surprise cover of the Beatles’ White Album in its entirety.

On New Year’s Eve 1999 they hosted The Big Cypress festival in the Florida Everglades, where they played from midnight to sunrise before tens of thousands of fans to usher in the new millennium.

And in 2017 they famously played a string of themed shows over 13 nights at Madison Square Garden — an event nicknamed the “Baker’s Dozen” — which included a different donut served to the audience each night.

In an era of tightly scripted concerts, this playful, unpredictable approach has endeared them to fans.

“Every single show is different, and they keep challenging themselves to be better,” said longtime Phish fan Andy Bernstein, who authored the first edition of The Pharmer’s Almanac, an encyclopedia that compiles the band’s history and statistics.

“They built an incredible bond with fans by super serving their audience,” said Ari Fink, senior director of music programming at SiriusXM Radio, where he worked with the band to create a Phish radio channel.

Fink says he understands the band’s non-traditional music may not be accessible to casual listeners.

“I can totally understand the barrier of entry that some music fans might experience when they give Phish a shot, but the playfulness and the commitment to their craft are the two benchmarks they bring to the table,” he told CNN.

The band’s members have been through a lot together

After their sold-out shows at Sphere, where top seats are commanding more than $2,000 on the secondary market, the quartet plans to go back on the road for another summer tour this July. The same month they also plan to release “Evolve,” their 16th studio album.

In August Phish are scheduled to host the Mondegreen festival in Delaware, their 11th self-produced large festival, a tradition the band started in 1996 by taking over a decommissioned Air Force Base in upstate New York.

No band endures for four decades without some turbulence, and Phish is no different. Anastasio battled drug and alcohol abuse before getting clean in the mid-2000s. The band took several hiatuses, and its future once was unclear.

But the four musicians have persevered, and they say their brotherhood has deepened over the years. Anastasio says his level of awe for his bandmates has grown consistently since they met as teenagers, and they all feel immense gratitude that they still get to create magic together onstage.

“The amount of material and the amount of shared history is just incomprehensible at this point in time. I’m trying to find some wood to knock on, but it doesn’t seem to be slowing down at all,” he said.

“Walking on stage has become consistently more emotional as the years have gone by, like we look at each other before we go on,” he said. “I can’t believe I have another chance to play with these guys, wherever we are.”

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