The Curious Case of Benjamin Button

French composer Alexandre Desplat has faced his share of eclectic challenges — from “Birth” to “Syriana” to his Oscar-nominated “The Queen” — but rarely one as difficult as “The Curious Case of Benjamin Button,” David Fincher’s epic adaptation of the F. Scott Fitzgerald short story about a man who ages in reverse.

“The character is an innocent watching life around him. How do you show his soul with music?,” the composer asked. “How do you manage on a long story — the life of a man and all his various encounters, sad or joyful or thrilling or dangerous — to find a musical path that progresses?”

Subtlety and restraint were the bywords, he says. “Don’t think lush, huge orchestral score; think lush chamber-music score,” he explains. “The detail is very important. All these colors, as in a chamber group, answer to each other: The trumpet will dialogue with the flute, the saxophone with the viola or cello, all very interwoven.”

The music didn’t have to reflect the period, he and Fincher decided. “We’re following his soul, not the world around him,” Desplat adds.

Fifty strings, two harps and various keyboards that could “play in a transparent way, and still give the notion of movement and time passing,” were critical, he says. “Instead of overwhelming the soundtrack with music, you have to keep quiet but (with) very strong musical energy. It’s more of an undercurrent in the movie.”

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