When it happened it was an unexpected and unlikely collaboration but it works and minimally if there is anything you give Kanye West, it's his penchant to push boundaries. Thus, when he started collaborating with legendary Paul McCartney as much as it was a surprise it really wasn't. Paul even went as far as to compare working with Ye to his experiences working with John Lennon.
Shoutout to the internet one time because Complex came across a redditor that has unearthed a video of McCartney performing a song called "Two Fingers." You will find a very familiar, whistled riff at the 1:13 mark. Seemingly, McCartney's contribution to Ye's "All Day" came from an unreleased song from the '70s. After "Two Fingers," McCartney used the chords for the track "When the Wind is Blowing," however, being that it was being recorded for a film that never came to fruition, the song was never officially released beyond teasers. And now, in 2015 what started as "Two Fingers" in 1970, was repurposed and unreleased as "When The Wind Is Blowing" is now a single of one of the year's most anticipated albums, Kanye West's Swish.