Sir Paul McCartney felt ''nervous'' about collaborating with Kanye West.

The music icon and Kanye, 40, worked alongside Rihanna on the 2015 hit 'FourFiveSeconds' - but Sir Paul has admitted to harbouring doubts about the project prior to meeting the controversial rap star.

He explained: ''I got a phone call and my manager said, 'Kanye West would like to work with you.' And I go, 'Yeah, we'll do it.' I was a little bit nervous at first, because I thought it could go horribly wrong. But I was intrigued to see what he was up to and how he did it. And it was a very intriguing process.

''You basically don't write songs. You basically just talk and noodle a bit and you record it all on your phone. And then he goes away. And that's basically his record. But it was great doing it because I don't work like that.''

However, Sir Paul admitted there are some parallels between how Kanye prefers to work and the way The Beatles made their iconic 'Sgt. Pepper's Lonely Hearts Club Band' album.

Speaking to comedian Tim Minchin, Sir Paul shared: ''I was waiting three months after we'd finished. I didn't really hear anything but 'Hey, bro, what's going on?' But I'm thinking, should I say, 'Did we write a song? Will a record come out of this?'

''Anyway, this arrives and it's a Rihanna song ... I said, 'This is great! I have to ring up and say, 'Am I on this?' And he goes, 'Oh, yeah. You're the guitar player.' I go, 'I don't remember.' And he said, 'We sped it up.'

''So they manipulated this kind of ... although, we're talking about 'Sgt. Pepper,' we loved manipulating. So I think we would have been into a lot of these tricks nowadays because we did speed things up a little bit.''