NEW YORK – It starts with the frantic tapping of a typewriter. Then a piano enters with its own tapping – a note repeated, quietly and nervously, 16 times against the irregular mechanical beat. As the duet joins in lockstep, a ponderous melody arrives, constantly building tension.

Call it a brief overture to a tale of two keyboards. The keyboards are actually musical representations of the two rival sisters in “Atonement,” the tragic, Oscar-nominated World War II love story.

The typewriter symbolizes the jealous younger sister, Briony. Using a 1935 Corona, the composer, Dario Marianelli, recorded the individual taps on a computer. That enabled him to adjust the pulse, volume and even the ring at the end of the line and the ripping of the paper from the carriage.

It was Briony’s writing that set the romance between her sister, Cecilia, and Robbie on its tragic course.

The score by the 44-year-old Marianelli, who was born in Italy and has lived in England for 18 years, is up for an Academy Award on Sunday. It’s one of seven Oscar nominations for the movie directed by Joe Wright. Marianelli’s music has a good chance against “The Kite Runner,” ”Michael Clayton,” ”Ratatouille” and “3:10 to Yuma.” It’s already won awards at the Golden Globes and British Academy of Film and Television Arts.

Marianelli, whose score for “Pride and Prejudice” lost in the 2005 Oscar contest to “Brokeback Mountain,” spoke in a recent telephone interview from London about “Atonement.”

AP: Did you expect to get nominated again?

DM: You never expect something like that. It was wonderful when the Golden Globe nomination came and I thought this was good, people are noticing. … I think because of the typewriter there has been a certain amount of attention.

AP: It certainly captures the character of Briony.

DM: The idea came because of the theme of the movie. You start the movie with somebody typing and already you see a bit of fiction within the fiction of the film. But it also captures something in Briony’s character. … There’s something almost mechanical about her at times. She’s almost like a mechanism that has gone slightly wrong and she becomes obsessive about things. It’s like some little cog gets stuck in her mind.

AP: It’s also playing against this lush music from the piano and orchestra.

DM: It’s the perfect contrast to the love story, which is the other side of the film. There can’t be anything more removed from the mechanical clackiness of the typewriter. The Rob and Cecilia story is a very British love, a story of love unfulfilled. … We started looking at (David Lean’s 1945) “Brief Encounter” as the only other great example of a British movie where love could have happened but didn’t happen. But it happens in the movie in some way.

And so it’s the music that’s lush and romantic and passionate. When you’ve had characters that are quite repressed and contained, and even the acting is very restrained but not the music.

AP: One exceptionally romantic track on the CD is “Love Letters.” It’s a cello and piano duet, very Brahmsian, like a third cello sonata, which Brahms never wrote.

DM: I wrote this piece thinking when I get to see the film, I’ll see if there’s a place I can put it. As hard as I tried to find a place in the film to put that, it never worked because in fact the narrative within the music is too strong. That’s why it ended up in the end credits because we didn’t want to lose that piece. It seemed to capture something about the film, something about the love story.

In my days as a pianist I played enough Brahms. There was enough left in my hands to regurgitate it in some way.

AP: Actually in the cut “Briony,” I hear the triplets of the strings from the scherzo movement of Beethoven’s Ninth. Were you drawing on that consciously?

DM: Not consciously. If it becomes conscious then I stop myself. I wouldn’t consciously set out to imitate a piece of music on an existing style. In fact I quite dislike the word “style” altogether because to me, the moment where you’re too aware of the style then it becomes a superficial.

AP: What about the Dunkirk evacuation scene? It was so emotionally powerful.

DM: For a long, long time Joe didn’t want any music there. He was convinced that this scene was playing perfectly well without any music, just with the choir coming from the soldiers singing (the 19th century hymn, “Oh Thou, oh Lord Father of Mankind.”) …

I started putting some pressure on him to let me have a go at least. And then eventually he accepted. The first couple of goes weren’t particularly successful, but he could see where I was trying to go. The idea of incorporating the hymn within the music was there from the beginning. It was an interesting idea, interesting enough to keep going until eventually we got something we were really happy with.

AP: Do you plan to expand the music, maybe your own cello sonata?

DM: I’ve just turned it into a cello and piano suite, at the request of Caroline Dale, who plays the cello on both “Pride and Prejudice” and “Atonement.” She asked for a concert piece to play of the music for “Atonement,” so I’ve turned it into a cello and piano suite of about 35 minutes.

AP: What about the rest of the soundtrack? Are you planning on making it more suitable for the concert hall?

DM: There have been a few requests. The problem is I haven’t had a lot of time to pursue this. The moment it comes as a commission it would probably focus my mind.