The second in a four-part series looking at the origins of some of the world's most popular melodies:

Was there ever a real Holly Golightly? Apparently, yes. American Dorian Leigh Parker started modelling in the 1940s at the late age of 27 but, with a face that was classically-boned, eyes of hypnotic blue and an air of feminine mystery, she quickly became the most famous model in the world.

During her long life of more than eight decades, Dorian Leigh (who dropped her surname when she first started modelling) had several husbands and a legion of A-list affairs. Truman Capote became fascinated with her, and was a frequent visitor to her New York apartment.

The story behind the song: Happy Birthday

He learned to gain entry through the fire escape, and she would come home to find him playing with her cats. Capote coined a nickname for her, "Happygo- lucky", and inside his head a character began to form – a woman with a more than liberal take on the rules of life.

Thus was born one of the memorable characters of 20th-century fiction, Holly Golightly. She was introduced to readers when Capote's Breakfast at Tiffany's was published in 1958. It was a remarkable book, and risqué for the 1950s: Holly has no compunction about mentioning her adventures in bed, she accepts that black men can be attractive, and lacks any guilt about stealing a friend's man.

Word spread very quickly that Holly was directly based on Dorian Leigh. Work soon began on the movie, which was released in 1961. Capote wanted Marilyn Monroe to play Holly Golightly. But he was overruled by executives at Paramount, who contracted Audrey Hepburn.

Initially dissatisfied with the leading lady, Capote was even more horrified at changes made in his story – the whitewashing of Holly's moral freedoms, and particularly the ending, where Holly was persuaded to remain in New York. But nobody had any complaints about the choice of the movie's composer and lyricist.

Henry Mancini and Johnny Mercer had impeccable track records. The former had been responsible for the Pink Panther theme, the latter had provided the words for Hooray for Hollywood, One for My Baby and a dozen others.

Mancini and Mercer were eventually awarded four Oscars each, including one, in 1962, for best movie song with Moon River, from Breakfast at Tiffany's. Audrey Hepburn's singing voice was threadlike, and extremely limited in range, though always in tune. But Mercer faced some obstacles in getting to a final concept of a song for her.

He had grown up in Savannah, Georgia and, with memories of its waterways, started a song called Blue River, but discovered that the title was already in use. He tried using the opening words "I'm Holly" but discarded that as banal.

Mancini took a month to compose exactly the right melody to suit the waif-like good-time girl. In the movie, Hepburn sang the song herself, sitting with a guitar on the fire escape of a New York apartment, and the result was charming.

Mancini later reported that after the very first preview screening of the film, the president of Paramount Pictures puffed a cigar and announced that the song had to be removed. The normally gentle Hepburn told him firmly that it would be over her dead body.

In spite of the movie's success, Paramount still seemed cagey about the actress's singing and on the "soundtrack" album, her simple vocal-plus-guitar was replaced by a sweeping Mancini orchestral version. But, with or without Hepburn, the song soared in popularity.

In the first flush of its release, more than a million copies of the sheet music were sold. Andy Williams's recording and subsequent performances became one of his biggest hits and the song title became the name of his own theatre in Missouri, which also features a Moon River Grill.

Five hundred other known recorded versions exist, including those of Frank Sinatra, Louis Armstrong, Judy Garland, Sarah Vaughan and Sarah Brightman. After Hepburn died in 1993, her own original track was released for the first time. And a large river inlet in Savannah, near where lyricist Johnny Mercer lived, was renamed Moon River in his honour.

Moon River crops up in unexpected places. Movies made as far afield as Japan and Korea have featured it. It has been heard in the television series Sex and the City and The Simpsons. In the 1985 movie Fletch, Chevy Chase croons the tune while having his rectum examined, and comedienne Joan Rivers has presented her own selfdeprecating version: "Joan Rivers, older than the sky…" People have sometimes asked about the meaning of the phrase "huckleberry friend".

As a child, Mercer picked huckleberries (like wild blueberries) in the summer. To him, the berries had a personal connection with a carefree boyhood, strengthened by association with Mark Twain's character Huckleberry Finn.

The implication was that Holly Golightly, who was actually of hillbilly stock, and Huckleberry Finn might well have been friends, if ever they had met.