In an alternate timeline, Earth was gifted with a full-length Paul McCartney and Kanye West collab album back in 2015 featuring at least one instance of Ringo Starr drumming over some carefully selected Beatles and Wings samples. Ideally, the samples in question would have been "A Day in the Life" and "Band on the Run."

Clearly, we aren't living through that particular timeline. We did, however, get a run of McCartney x West collabs in 2014 and 2015 including "Only One," "FourFiveSeconds" with Rihanna, and the Grammy-nominated "All Day." In a new interview, McCartney—whose just-announced album Egypt Station is out soon—detailed what he learned during his unconventional writing sessions with West.

"With Kanye, I learnt a lot," McCartney, who was a already a "big fan" of MBDTF and WTT before West hit him up about working together, told DIY Wednesday. "We had a method in our early days of The Beatles and with Wings that I used all the way through for writing songs. I would sit down with a guitar or at a piano and make it up and complete it. Then that's it, you've done your song, and then you're ready to roll and go in the studio." For his sessions with West, the approach was even looser.

"With him, it was much more made up as we went along—so much so that I didn't even realize that I was making songs," McCartney explained. "We had two or three afternoons where we just hung out together in a Beverly Hills hotel in the bungalows out the back, and he had his engineer and was set up with a couple of microphones in case anything happened. I was tootling around on guitar, and Kanye spent a lot of time just looking at pictures of Kim on his computer. I'm thinking, are we ever gonna get around to writing?! But it turns out he was writing. That's his muse. He was listening to this riff I was doing and obviously he knew in his mind that he could use that, so he took it, sped it up and then somehow he got Rihanna to sing on it. She's a big favorite of mine anyway, so that just came without me lifting a finger."

Later, McCartney revealed that he recently looked up the writing credits for "All Day" and was surprised to see none other than Pulitzer Kenny on the list. "There were only three of them I knew and one of them's Kendrick Lamar!" he said. "I'm thinking, I've written a song with Kendrick Lamar? I wish I'd met him! But that's just the way they do it these days." The inclusion of one of McCartney's favorite bands—Dirty Projectors—on "FourFiveSeconds," he added, was also a post-release surprise. Catch the full DIY chat here.

McCartney's Egypt Station, featuring the simultaneously released singles "I Don't Know" and "Come On to Me," is out Sept. 7 via Capitol.