Bon Iver worked on "at least 10 songs" with Kanye West, the indie folk act has confirmed, joining artists like Beyoncé, Jay-Z and Nicki Minaj on the rapper's upcoming album. "[Bon Iver's] similar to me," Kanye West explained this week. "He just does shit just so people [will] be like, 'Oh shit, how did you do that? How did that happen?'"

When rumours broke of a collaboration between West and Bon Iver, fans scarcely expected such a quick confirmation – and from both sides! But both West and Bon Iver's Justin Vernon have already gone on the record, talking about hanging out, smoking up, making music and playing basketball. In a new interview with Pitchfork, Vernon described three separate week-long trips to West's Hawaii studio, working as a kind of amped-up session musician. "I was literally in the back room rolling a spliff with Rick Ross, talking about what to do on the next part of a song," he recalled. "It was astonishing."

Speaking to Rolling Stone, West said he was introduced to Bon Iver's melancholy by the owner of French label Ed Banger, Pedro Winter. Winter played him the song Woods, an Auto-Tune-heavy track from Bon Iver's Blood Bank EP, explaining plans to sample it. West allegedly asked if he could use the sample instead – and next you know it, he was ringing Wisconsin. "I called [Justin] and we ended up becoming like really good friends, playing basketball together everyday, and going into the back studio [to] just record his parts," West said.

Vernon recalls that first conversation. "[Kanye] was like, 'I like how you sing so fearlessly. You don't care how your voice sounds. It'd be awesome if you could come out to Hawaii and hear the track, and there's some other shit I think we could throw down on.' I was just like, 'Yeah, cool man!'" Vernon ended up contributing more than a stale sample – he arranged new "choir-sounding stuff", "thickening out" vocal parts, writing hooks. West even gave him a separate studio, a "tiny back room", to record ideas. "It was fucking fun, man," Vernon said. "Just a bunch of uber-talented people and everyone was really nice and chill and just working on Kanye's record."

At least one of these collaborations, a "festival closer" song called Lost in the World, is a lock for West's album, due 16 November. But others could appear, too. More weirdly still, this may not be the end of Vernon's hip-hop adventures: "Shit's ... coming in," he said. "I could probably have some shit lined up to work on if I wanted to have a bunch of kids and not tour again."

In other up-to-the-second Kanye West news, the rapper has proposed that he and Wu-Tang Clan founder Raekwon make a song with teen singer Justin Bieber. "EPIC," Bieber declared. At a New York club, West also debuted another new song, Mama's Boyfriends, featuring a prominent sample of Billy Joel's Movin' Out. Say what you will about Ye – it's all curiouser and curiouser!