N E W Y O R K, May 1, 2001 -- The famous pop lyric "Ob-la-di, ob-la-da, life goes on …" didn't come to Paul McCartney in dream. It came to him in a nightclub.

"'Ob-la-di' came from a guy in a nightclub I used to frequent," McCartney told ABCNEWS' Diane Sawyer. "He was a black friend a mine called Jimmy Scott. And I used to just say, 'What's happening, Jimmy?'"

McCartney says Scott, who had a strong Jamaican accent, would answer, "Ob-la-di, ob-la-da, life goes on, bra."

"And so I just thought, 'That's a great saying,'" said McCartney. "'Ob-la-di, Ob-la-da, life goes on, bra.'"

McCartney says he often created the characters in his songs — the same characters with whom his fans felt they could identify personally.

'I Just Make Them Up'

"I remember talking to George Harrison," McCartney said. "He was saying that he didn't write songs the way I did."

Harrison always writes from his own personal experiences, he said.

"He said: 'I don't know how you write this 'Ob-la-di, Ob-la-da,' 'Molly and Desmond … Do you really know these people?'" recalled McCartney. "I said, 'No, I just make them up, like a novelist makes characters up.'"

Blackbird Is a Woman

The title of McCartney's poetry book Blackbird Singing, released last month, comes from the Beatles' 1968 acoustic hit "Blackbird," on the White Album.

Talking with Sawyer, McCartney revealed the symbolism of the lyrics of that song, which includes the lines,

Take these broken wings and learn to fly All your life You were only waiting for this moment to arise.

"I wrote it in the '60s, when the civil rights movement was at its height," he said. "I liked to think of a blackbird as being a kind of symbol for a black woman."

Diane Sawyer's interview with Sir Paul McCartney continues all week on Good Morning America. On Wednesday, they discuss his love affair and marriage with Linda McCartney.

Diane Sawyer's interview with Sir Paul McCartney continues all week on Good Morning America. On Wednesday, they discuss his love affair and marriage with Linda McCartney.