The astonishingly prolific Alexandre Desplat scored the year’s biggest box office hit (“Harry Potter and the Deathly Hallows: Part 2”); one of the year’s most acclaimed films (“The Tree of Life”); and a last-minute entry (“Extremely Loud and Incredibly Close”) that could be on the list of year-end contenders.

Those are just three of the six Desplat films that will have seen domestic release before the end of December. The others: George Clooney’s political drama “The Ides of March,” Roman Polanski’s dark comedy “Carnage,” and the little-seen immigrant drama “A Better Life.”

As if that wasn’t enough, the Paris-based composer also penned a theme for “My Week With Marilyn” and scored two other films that didn’t get an American release: the action-adventure “Largo Winch II” and the French period piece “La Fille du puisatier.”

“Extremely Loud” is the wild card in the group. When Variety talked to Desplat in earlier this month, the composer was still in the midst of writing 70 minutes of music for director Stephen Daldry’s much-anticipated 9/11 film, which was to be recorded starting Nov. 10 in New York.

Desplat is a last-minute replacement for an earlier score by Nico Muhly (“The Reader”). “I got a phone call one day saying, ‘Are you free — now — to work on a crazy deadline?’ I could not say no, especially for Stephen Daldry.” Desplat described his score as variously “propelling, emotional, tender and sorrowful,” but few will hear it before mid-December screenings.

Desplat, a four-time Oscar nominee (for such films as “The Queen” and “The King’s Speech”), was named Film Composer of the Year for the third year in a row at this year’s Ghent Film Festival, dedicated to honoring composers.

Exactly what awards-season voters will choose among the composer’s output — and more precisely, what the Academy music-branch executive committee will decide is eligible — is hard to guess.

In all likelihood, the Acad will disqualify Desplat’s “Tree of Life” score as running afoul of the rule that prohibits scores “diluted by the use of tracked themes or pre-existing music.” Although Desplat wrote more than an hour of contemplative, impressionistic music for director Terrence Malick, only 14 minutes wound up in the final cut (the other 86 minutes consist mostly of classical excerpts, including Mahler, Bach, Brahms, Smetana, Mozart, Respighi and a healthy dose of Berlioz).

Composer and director talked frequently over a three-year period. “I read the script, then I saw some footage, but I never saw even a reel. I saw scenes, shots, bits and pieces. I never wrote to picture,” Desplat says, noting that he was always aware that his contribution would be part of a complex mosaic consisting of many composers’ works.

He remains in awe of Malick, whom he declares “a genius,” and offered the hope that “someday, somebody will play the film with the CD,” just to see how it might have played with more of his original music.

The emotional “Harry Potter” finale is another question mark for Acad voters. In this case, 92 of the film’s 104 minutes of music are Desplat’s (the remainder, mostly John Williams themes from the first film), but as the concluding half of a two-part film, will the branch committee declare it not an “original score”?

Potter fans worldwide, who used phrases like “tonal majesty” and “richly layered aural landscape” in reviewing Desplat’s work, would not take kindly to a disqualification and likely cite Howard Shore’s Oscar-winning third score in “The Lord of the Rings” trilogy as a precedent.

Desplat used a 110-piece London orchestra and 80-voice choir to close the Potter saga on a powerful note. In fact, he overdubbed his 60 strings as often as four times, “giving a great richness to the sound and to the counterpoint.”

The startling find of the “Part 2” score, however, is Desplat’s use of an almost impossibly pure solo voice to suggest the ghost of Harry’s mother, Lily.

It turns out to be that of Mai Fujisawa, the daughter of composer Joe Hisaishi, whose scores for the Japanese animated films “Princess Mononoke,” “Spirited Away” and others are international favorites. (She was singing on her father’s scores from the age of 4.)

Desplat’s alternately brooding and propulsive score for “The Ides of March” was the result of working on “Syriana” (on which Clooney was a co-producer) and meeting him later on “The Fantastic Mr. Fox.”

“George has a great sense of collaboration,” he says. “He comes with ideas and then you have to give them shape, make them evolve and blossom.”

The composer worked twice this year with Roman Polanski (on the heels of their much-admired 2010 collaboration on “The Ghost Writer”). He penned music for the documentary “Roman Polanski: A Memoir” and for the adaptation of Yasmina Reza’s play “God of Carnage.”

“It’s four people in an apartment, and they talk a lot,” notes the composer. “I said to Roman, you can’t have music inside the film. It’s got to book-end the film, just opening and closing, so that’s what we did.”

Desplat describes his “Carnage” music as “witty and angry,” like the play. But its brevity (seven minutes total) makes it an unlikely awards candidate.

Similarly, “A Better Life,” with its evocative acoustic-guitar solos for Los Angeles’ Mexican-American community, was a personal favorite for the composer but its modest box office and low profile are awards impediments.

Meanwhile, Desplat toils away on “Extremely Loud and Incredibly Close.”

Asked when he plans to take a vacation, he answers: “I am going to stop. One day.”

Eye on the Oscars 2011: Music Preview:

Silence is golden for ‘Artist’s’ maestro | Jonsi’s music animates Crowe’s ‘Zoo’ | From the Bard to Bean without missing a beat | Shoring up ‘Hugo’s’ ode to Melies | Spielberg and Williams duet for 25th time | Desplat’s impossible pace propelled into higher gear | Pix pulsate with driving electronica