Beatles legend Sir Paul McCartney has relied on "instinct" to write every one of his songs, insisting there's no formula behind his hundreds of hit tracks.
MCCartney is always amused when music scholars try to break down the tracks he composed with late partner John Lennon and his solo efforts, because he has no idea where they came from.
The singer-songwriter says, "I’m still intoxicated by the fact I can do it. If I were to try and answer how I do it, I couldn’t.
"I saw a guy on TV dissecting Penny Lane. He said, ‘MCCartney starts off in this key and then he modulates down to sing higher’. I’m going, ‘Did I? Brilliant, well done, lad!’ It’s all instinct. I just sort of do it."
MCCartney is still writing new material at the age of 67 and admits he's driven to carry on by his insatiable desire to try and better himself, adding, "Most artists I know feel like they have something to prove. That’s what keeps you going, that sense you can do it better. I mean, I remember not really liking the vocal on Eleanor Rigby, thinking I hadn’t nailed it.
"I listen to it now – and it’s very good. It’s a bit annoying when you do Eleanor Rigby and you’re not happy with it."