One of the most important collaborations in Hollywood is between songwriters and filmmakers. Music sets the tone for a film and highlights the story line. Mike O'Sullivan attended a recent Hollywood forum where composers explained how they write music for movies.

One classic collaboration was between the singing duo Simon & Garfunkel and the filmmaker Mike Nichols.

In the 1967 film The Graduate, music made performances by Anne Bancroft, Dustin Hoffman and Katharine Ross even more memorable.

Singer Jesse Harris wrote songs for this year's film The Hottest State, written and directed by Ethan Hawke. Harris performed two of them at the recent Hollywood forum.

The Grammy award-winning composer writes and records his own albums, but he also enjoys writing music for movies. He says each new song is a challenge.

"I try to make each song make sense for itself," said Jesse Harris. "So to me, each song dictates its own rules and its own direction. And I feel like the object is to find that, and then write the song."

Willie Nelson sings another Jesse Harris composition in the film The Hottest State, a sad song in keeping with the story of a young Texan in New York who struggles in his relationship with a beautiful singer.

Songwriter and record producer Glen Ballard worked with filmmaker Robert Zemeckis on the upcoming film Beowulf, based on the early Anglo-Saxon saga. The computer-animated movie features Angelina Jolie, Ray Winstone and Anthony Hopkins, and it needed some epic music.

Composer Ballard says music is a tool for the movie-maker, and a song or score has to fit the movie.

"A song in a movie has to do some serious heavy lifting, or otherwise it should not be there," said Glen Ballard. "So the idea that a song might be able to accomplish some story-telling, some character development, and whatever that song can bring to a scene - if it is going to be on-screen for a minute, it generally has to really work."

Getting the mood right can be a challenge. Norwegian singer Sondre Lerche worked with director Peter Hedges on the romantic comedy Dan in Real Life. plays a relationship expert who struggles to succeed as a single parent.

Lerche was on the set for the filming, and even taught the star how to play guitar. He says being there inspired him.

"I wrote one of the original songs for the sound-track in the house where it was filmed while they were shooting in the room next door," said Sondre Lerche. "It was a tremendous experience. That was my main inspiration, to be there."

This song was the result.

The director liked the song and put it in the movie.

These songwriters say their music adds an important dimension to films, allowing the composer to help with the narrative, and giving them an audience that might not otherwise hear their music.