Sir Paul McCartney talks to his guitars

Talking about one of his guitars, he shared: "I felt quite guilty in a minor way, so I went over and started playing - and then the song that came out was me talking directly to the guitar and talking about all the times it had helped me."

McCartney likened writing a song to sharing a secret with his guitar.

The Beatles star explains in a new book called 'The Lyrics by Paul

McCartney': "There's lots of stuff going on there.

"We always used to say that when you sit down with your guitar to write a song, you're telling it your secrets, which then become a song for the world.

"But at that moment, when you're alone, the guitar is your confidante.

You cradle it.

"When you go up to a piano, though, it's almost as if you're pushing the piano away; they're different actions completely."

Meanwhile, McCartney recently admitted he envied the Everly Brothers.

The chart-topping star revealed that that he and his former bandmate John Lennon were both influenced by brothers Don and Phil Everly, who made hits such as 'Cathy's Clown' and 'All I Have to Do is Dream'.

He said: "The biggest influence on John and me was The Everly Brothers.

"To this day, I just think they're the greatest. And they were different. You'd heard barbershop quartets, you'd heard the Beverley Sisters - three girls - you'd all heard that. But just two guys, two good-looking guys? So we idolised them. We wanted to be them."