Justin Vernon of Bon Iver performs at Wembley Arena in London, England. Credit: Courtesy of TNS

Justin Vernon of Bon Iver performs at Wembley Arena in London, England. Credit: Courtesy of TNS

Bon Iver has enjoyed one of the most enigmatic career arcs in music in the past ten years. What started as a group of bearded hipsters with acoustic guitars slung over their shoulders evolved into a factory of experimentation, then they disappeared. With the group’s impending release of new album “22, A Million” on Sept. 30, it is worth looking back at what got us here.

The first time most people heard Bon Iver was probably the strumming and ethereal vocals on “Skinny Love,” the pioneering song of the hipster-folk fad that spawned bands like Mumford & Sons and The Lumineers. “Skinny Love” is in line with the rest of the band’s debut album, “For Emma, Forever Ago.” Although it is easily the most accessible track, the others are minimalist, with bordering on sparse instrumentation, but they retain strong emotion that gives the listener the feeling of winter anytime of the year.

The band released a four-song EP of some truly lovely music the next year, including “Blood Bank,” one of its best songs. After that, things started to turn a bit toward the unexpected. Kanye West enlisted the leader of the group, Justin Vernon, to contribute to his 2010 album, “My Beautiful Dark Twisted Fantasy,” as well as sampling Bon Iver’s “Woods” on “Lost in the World.”

Vernon’s work on that album led to other collaborations with West, on “Watch the Throne” and
“Yeezus,” which included an amazing appearance on the raunchy “I’m In It,” and interplay with Chief Keef on “Hold My Liquor.”

Bon Iver returned with a self-titled, full-length album in 2011. “Bon Iver” was lush, mostly abandoning acoustic guitars in favor of other strings, and turning to synthesizers that, along with added effects, made Vernon’s voice all the more chilling. At this point, the band could hardly be categorized as folk any longer. Instead it became at times progressive or rock, ‘80s- and ambient-influenced.

It was hard for fans to see where they would go next. And so they didn’t go anywhere. “Bon Iver” was announced to be its last album, as Vernon and his bandmates faded into various outside projects. Vernon made an album with the band Volcano Choir, which, maybe only because of his distinctive vocals, felt like a fine substitute for a new Bon Iver album.

Whispers of new material started in the past two years, with live shows and rumors of a new album. The rumors were confirmed at Vernon’s Eaux Claires Music Festival, where tracks from “22, A Million” were debuted.

While it’s not yet released in its entirety, studio versions of three tracks have already been released, and many others have been heard live. The names of songs are enough to let you know that Bon Iver has continued along the line of experimentation.

“22 (OVER S∞∞N)” features one droning vocal sample in the background along with a single note and vocal sample in the foreground. Combined with with Vernon’s voice, guitar and horns, it makes for one of the strangest and most beautiful songs I have heard this year. “10 d E A T h b R E a s T” chops up pounding drums that turn triumphant beneath whatever effect is weaving in and out of Vernon’s voice. “33 ‘GOD’” is a mutated piano ballad with samples and other strange noises appearing and disappearing like hallucinations, before drums kick in and the listener’s adrenaline starts pumping.

They are three of the weirdest songs I have heard this year, and some of the best. Vernon was never the typical folkie with an acoustic guitar, that much was obvious even when he was making music that could be classified as folk. The sense of innovation and boundary-pushing in his music has expanded. The weirdness in his new music is so intricate that maybe Bon Iver was never going away, it just needed the last five years to put these new songs together.