By Chris Leggett BBC News entertainment reporter

Shore's credits include Philadelphia and The Silence of the Lambs

A memorable soundtrack - such as Bernard Herrmann's score for Pyscho - can help ensure a good movie becomes a classic film.

David Arnold, whose string of big screen soundtracks includes the last three James Bond movies and Independence Day, says composers are under increasing pressure.

He told the BBC News website: "New technology has meant that composers can now be asked to present their score in a demo form on synthesisers before it's been properly recorded.

"They then ask test audiences what they think. It is like judging a film by having the cast shout out the script first.

"People have been taken off films on the basis of the results. It is not a particularly rational form of decision-making."

David Arnold is writing the music for Daniel Craig's debut as Bond

Arnold says some of his most enjoyable work has been on low-budget movies.

He says: "If you get involved with Hollywood films where a lot of money is riding on them, you have to be prepared for all the stuff that goes with it.

"It tests every aspect of you, your tenacity and originality, your stamina and your sense of humour.

"Writing music is an emotive experience. When you get opinions from somebody you have never heard of, it is sometimes not the easiest thing."

Oscar success

The first female composer to win an Oscar, Rachel Portman, knows what it is like to see her services withdrawn close to the release date.

Rachel Portman's credits include The Human Stain and Ratcatcher

Ms Portman, who won the best original music score Academy award for Emma in 1997, says: "I've been in the situation where my music has been taken off a film twice, early on in my career.

"They were both films with problems. If a film is about to come out, changing the composer is one of the cheaper ways you can give it a facelift."

Ms Portman, who received further Oscar nominations for Chocolat and The Cider House Rules, says being dropped from a film can be "devastating" for a composer.

Ms Portman, whose credits include the recent Roman Polanski version of Oliver Twist, the remake of The Manchurian Candidate and Mona Lisa Smile, says she likes to have a close relationship with a director.

She says: "It's much easier to be answerable to one person.

Electrifying feeling

"Some directors like to get composers in for pre-production work, others book them up and then get them to come in when editing is underway."

Bernard Herrmann's Psycho score is among the most famous

She believes writing for film is worth the potential stress.

"To see a film without music and then furnish it with a score is electrifying.

"It's the most wonderful, creative process.

"A lot of people are interested in film music because it's classical music but a lot simpler than the kind of intellectual music that the majority of the public would find inaccessible."

Lyricist Don Black won an Oscar in 1967 for the song Born Free with composer John Barry, his long-time collaborator.

Near misses

His other successes include the theme songs for Diamonds Are Forever and Ben, hits for Shirley Bassey and Michael Jackson respectively.

"All the great film composers have been replaced on movies," he says.

"It happened to my friend like Elmer Bernstein, who did the Magnificent Seven and The Great Escape, on Gangs of New York."

Black says his most famous songs nearly did not see the light of day.

"The song Born Free was pulled from the soundtrack before the film was premiered but then it became a hit single so it had to be added to every print.

King Kong was recently voted the most terrifying movie monster ever

"Harry Saltzman didn't like Diamonds Are Forever because he thought the lyrics were too explicit but Cubby Broccoli did.

"You could make a great album of the soundtrack music that was never released."

Professor Mervyn Cooke, who teaches film music at Nottingham University, says there is a historical precedent for the King Kong change.

"When the original film was screened to test audiences, people laughed at the gorilla," he says.

"It looked like a puppet or a man in a costume so composer Max Steiner was brought in.