What do Bon Iver, Spike Lee & the Grateful Dead have in common? Piano man Bruce Hornsby

What do Bon Iver's Justin Vernon, Grateful Dead lyricist Robert Hunter and filmmaker Spike Lee have in common?

They all had a hand in Grammy-winning pianist Bruce Hornsby's daring new album, "Absolute Zero." As you can imagine, it's stylistically unclassifiable and enrichingly trippy.

Hornsby has been scoring Lee's projects — mostly his indie films and the Netflix series "She's Gotta Have It" — for over a decade. They met when Lee directed some videos for Hornsby in 1995.

"I've written 230-plus pieces of music [for Lee] ranging from 1 minute long to 4 minutes," said Hornsby, who performs Friday at the Pantages Theatre in Minneapolis. "Lots of these instrumental pieces — we call them cues — are fully formed. They wanted to be developed into songs.

"Fully six or seven of the songs on 'Absolute Zero' have their origin in Spike Lee film cues." It was a "crazy, intangible, strange process," he said, "putting words to an already completed musical picture."

His process with Hunter is also unconventional.

The pianist, who toured with the Dead from 1990 to '92 and has since sat in with various Dead musicians, had teamed up with Hunter on three previous pieces before working on "Take You There (Misty)" for this new album.

Hunter reached out to him in 2008. They've been writing long-distance ever since.

"It's a bit like Elton John and Bernie Taupin in the sense that Bernie would write the lyrics and send them to Elton," said Hornsby. "I haven't seen Bob Hunter since 1997 at the second Furthur Festival at Alpine Valley" in Wisconsin.

As for Vernon, the Bon Iver frontman has long been a fan of Hornsby. In 2015, he invited the pianist to join him for "Black Muddy River" on a Dead tribute record. The next year, Hornsby performed his entire 1986 debut album "The Way It Is" at Vernon's Eaux Claires festival. In 2017, Hornsby was a special guest during Bon Iver's performance at the Coachella fest in California.

"When Justin starts singing in an isolation booth [at a recording studio], the air changes in the room," Hornsby observed. "There's excitement and possibilities because he's such a creative force. He has his own unique vision and approach. He brings a ton to the table. And he's a great person and a great hang. That's a fairly unbeatable combination."

Other Eaux Claires performers ended up on "Absolute Zero," including the Brooklyn chamber group yMusic and British harmonizers the Staves as well as guitarist Blake Mills, esteemed jazz drummer Jack DeJohnette and Twin Cities musicians Mike Lewis (saxophone), JT Bates (drums) and Jeremy Ylvisaker (guitar).

Vernon and Hornsby have worked on several tunes together. Hornsby appears on Bon Iver's new single "U (Man Like)" — from the group's fourth album, "I, I" (due Aug. 30) — while Vernon sings on Hornsby's new "Cast Off." Both were recorded last year in Vernon's studio near Eau Claire, Wis., along with about five other tunes.

Will Vernon, who often hangs out in the Twin Cities, show up at Hornsby's gig?

"I'm not one to reach out to people and say 'Why don't you come over here?' " said Hornsby. "It would be on a whim or audible call by Justin."

Bon Iver drummer and vocalist S. Carey is opening for Hornsby. He, too, performs on "Absolute Zero."

"He sang beautiful ethereal background vocals on the outros on my record," said Hornsby. "I'd love for him to jump in. I'm always open to it."

That's the thing about Hornsby — he welcomes collaboration and he loves improvisation.

In fact, his signature hit, "The Way It Is," was, as he describes it, a folkie tune about racism with two jazz piano solo improvisations. "That is hardly a formula for pop success," he pointed out.

His 20 studio albums have explored jazz, electronica blues, Americana, bluegrass (with Ricky Skaggs), Appalachian (he played dulcimer) and all kinds of experimental sounds influenced by everyone from Steve Reich to Father John Misty.

"I'm everywhere and nowhere," he said with a chuckle. "I'm not part of any club. I've always been creatively restless."

In addition to his own projects, Hornsby, 64, has been an in-demand studio pianist, recording with Bonnie Raitt (on "I Can't Make You Love Me"), Don Henley (they co-wrote "End of the Innocence") and Bob Dylan (the album "Under the Red Sky").

One time during a Dylan recording session, Hornsby was jamming on a chord with bassist Randy Jackson, drummer Kenny Aronoff and guitarist Robben Ford.

"And Bob walks in," Hornsby recalled. "He had all these lyric sheets — written on everything from hotel paper to napkins — spread out on a table. He looked around and picked a lyric and just started singing to this track. That became a song on the record called 'T.V. Talkin' Song.'

"He's a spontaneous improvising musician. I feel a kindred spirit that way."

Twitter: @JonBream • 612-673-1719