Composer Henry Mancini wrote “Moon River” specifically for Breakfast At Tiffany’s star Audrey Hepburn. He said, “It’s unique for a composer to really be inspired by a person, a face or a personality, but Audrey certainly inspires me. Normally, I have to see a completed film before I’ll compose the music, but with Breakfast At Tiffany’s I knew what to write for Audrey just by reading the script.”
Since Hepburn had no training as a singer, the vocals were written to be sung in only one octave. Mancini said that while many versions of the song have been done, he feels that Audrey’s was the best.
It was director Blake Edwards who brought Mancini into the project, after Mancini had scored a hit with the theme from Peter Gunn (1958), though the producers were initially keen on a Broadway composer to fit the New York City milieu of the film. Mancini brought in Johnny Mercer as his lyricist, and so “Moon River” was born. Early titles for the song included “I’m Holly” and “Blue River”.
At a post-production meeting following a screening of the film, a studio executive, in reference to “Moon River,” said, “Well, I think the first thing we can do is get rid of that stupid song.” Audrey Hepburn stood up at the table and said, “Over my dead body!” However, there’s an alternative recollection of this event. On the DVD of “Breakfast at Tiffany’s Anniversary Edition,” co-producer Richard Shepherd says in his commentary that after a premiere in San Francisco, Paramount’s Head of Production desired to have “Moon River” removed from the film but co-producer Martin Jurow “and I both said ‘over our dead bodies.'”
In the book for Breakfast At Tiffany’s. the narrator describes how Holly would wash her hair and sit out on the fire escape thumbing her guitar while waiting for her hair to dry; which explains why when she sings ‘Moon River’, she has a wrap around her hair.
Author Truman Capote envisioned Marilyn Monroe in the part of Holly Golightly. Monroe was originally cast as Golightly, but her drama coach, Lee Strasberg, told her that playing a call-girl was not good for her image. The film went on to be a huge success, with Monroe’s replacement Audrey Hepburn receiving Golden Globe and Academy Award nominations for Best Actress. – Edited from IMDB