Sir Paul McCartney has spoken about some of his songwriting secrets ahead of the release of his latest album, Chaos And Creation In The Black Yard.
McCartney says he does not like to over-analyse his songs
The album is Sir Paul's 20th studio recording since he left The Beatles, and was produced by Nigel Godrich, known as Radiohead's "invisible sixth member" and who has also worked with REM Travis and Beck.
The musician told Radio Four's Frontrow that Godrich had made a massive difference to the sound of the album.
"The good thing about working with Nigel in this case was that I would bring in something - a song, a certain idea of how it might be treated - and he would say, 'look, that's a little bit ordinary - let's look at it a bit differently'," he said.
"There's one song, called How Kind of You - the second song on the album - and I brought it in as a strummy sound, but Nigel said, 'you can do that - but let's look at putting a kind of ocean down, a sort of bed.
"So we got drones going, and a harmonium and piano loop. It removed it from the ordinary."
Lyrically, Chaos And Creation In The Back Yard addresses just one person, in a way similar to some concept albums.
However, Sir Paul insisted that it was never possible to work out how an album would turn out.
"You never know quite what you're doing, because you never step back and go, 'ah, I see the concept'," he said.
"You just write a few songs, and the mood you're in, and the time and space you're in, governs that."
Godrich made his name producing Radiohead's OK Computer
He said that, for example, one song, Jenny Wren - which McCartney describes as the "little sister" of the Beatles song Blackbird - was inspired by him seeing a flute player with Ravi Shankar at the Royal Albert Hall.
"I saw this guy on this low, mournful Indian flute. I traced him down through Ravi, because he had a sound that I wanted for the album, and found he was actually a Venezuelan guy called Pedro Eustace and that the flute itself was an Armenian instrument."
He also explained how the musical relationship of the song to Blackbird came about.
"In Blackbird, it's a particular style, it's almost like a folky style - but I can't actually do the proper fingerpicking style that real fingerpickers will do, so I've invented my own fudge of it," he said.
"That style of playing originally came from me and George [Harrison] having a party piece when we were kids, which was a piece by Bach.
"I thought that I loved doing that Bach thing - George did it better than me, he could do the real thing - but that was my goof of it."
Sir Paul's way of playing the Bach gave him a melody and a bassline together, which was the origin of Blackbird.
But he never revisited this style until the new album, when he worked on the song Jenny Wren sitting in his car in Los Angeles.
"It was just the finger-style thing - I just thought I fancy doing something in that style," he added.
He also said that he still has songs which wander through his mind, or he wakes up with the opening line in his head.
He is able now to record them on tape at the time - but said that when he was with the Beatles, this was not possible, and this was how he and John Lennon would know if they had a good song.
"The great thing about John and I in the old days was that we didn't have tapes - but that was great because it focused us," he said.
"We used to say to each other, 'if we can't remember it tomorrow, it's no good.'
"How memorable is a song that you wrote last night and you can't remember this morning? It's not good."
But he added that he felt analysing his songs too much "spoils it".
"It's magic to me," he said.
"This whole process is completely magic, and I always feel like someone is going to catch me and stop me doing it for a living.
"There's always that feeling that this is too good to be true. So I don't want to tempt fate."