When Lynn Novick, Ken Burns’ longtime filmmaking partner and creative collaborator during the 10-year making of The Vietnam War, went to see The Girl with the Dragon Tattoo, David Fincher’s 2011 remake of a Nordic-noir classic, she pretty much knew what to expect: an Americanized take on a pop-cultural sensation in Europe, with Daniel Craig in the role originally played by the late Swedish actor Michael Nyqvist.

Novick says she found the film mildly diverting — the critics’ consensus at the time was that, while Fincher is a master stylist, the Danish original was superior in virtually every respect — but one aspect of Fincher’s Girl with the Dragon Tattoo rocked her back. The background music score, by Nine Inch Nails’ frontmen Trent Reznor and Atticus Ross, was a living, breathing character in its own right.

At the time, Novick and Burns were wrestling over the  problem of the musical tone for The Vietnam War, their 18-hour, 10-night documentary that debuts Sept. 17 on PBS.

Burns knew all along that he would use as many appropriate songs of the era as he could snag the rights for on a PBS budget, but the background music — music that sets the tone, without being obvious or intrusive — was proving to be a thorny issue. Somehow, the harmonies and folk music that underscored his seminal series The Civil War just wouldn’t cut it for a docuseries as contemporary, topical and nerve-inducing as The Vietnam War.

You really need to listen to this, Novick remembers telling Burns, of Reznor and Ross’s music for Girl with the Dragon Tattoo.

Burns agreed — but there was little likelihood that composers as established on the big screen as Reznor and Ross would agree to work on a modestly-budgeted documentary series for PBS, even if said documentary did have the imprimatur of the filmmaker behind The Civil War, Jazz, Baseball, Prohibition and The Dust Bowl, among others.

Only a funny thing happened.

Reznor and Ross (with Burns and Novick, right) agreed. They were privately humbled and flattered to be asked, and didn’t have to think too hard about it.

But then the work began. And much like the film itself — 10 years in the making, remember — composing the music for The Vietnam War took on a life of its own.

This wasn’t going to be the traditional big-screen film approach of coming up with a recognizable theme, and then playing variations of that theme over the course of a two- or three-hour film. This was going to be 18 hours, and the backdrop would range from Southeast Asia to the halls of power in Washington, DC, university campuses from Berkeley to Kent State, and bucolic, small-town homes across the U.S. midwest. The music would need to span more than two decades of American history, and there were more than a few moments when Reznor and Ross wondered what on earth they got themselves into.

“Part of what is so difficult about Vietnam is that there’s not just one truth,” Burns told reporters earlier this year, at the semi-annual meeting of the TV Critics Association. “Wynton Marsalis said in our Jazz film that sometimes a thing and the opposite of a thing are true at the same time. These two men understood that. And the soundtrack they delivered permitted us to have not only the discomfiting anxiety of feeling what this world was about but, underneath that, a kind of melodic and emotional core.

“I'm an emotional archaeologist. They were able to convey both the reality of the Vietnam War to us, but also the underlying sense of possibility and hope.”

Burns is a name familiar to almost anyone who’s watched television in the past 27 years, but he will tell you — and his Vietnam War partner Novick will concur — that filmmaking, at least the way he does it, is a collaborative medium.

Burns, Novick, producer Sarah Botstein, historian and writer Geoffrey C. Ward and a small army of technicians and creative artists would sit in on long meetings in a conference room, compare notes and hash out problems together.

The final decision rested with Burns, and Novick, but the process was essentially collaborative. When you work on a Ken Burns film, you check your ego at the door. Over time, Reznor and Ross realized they were part of something truly special.

“(Burns and Novick’s) style of working complements our own,” Reznor (on the right, with Ross) said. “We were able to disappear over, for us, a lengthy period of time and create music from an impressionistic place, a place that was really from the gut. We tried to immerse ourselves in these different sentiments that they were looking for,  and create long pieces of music that we would then  entrust with them and their editing team, placing and weaving in amongst music from the era and some other material that Yo_-Yo Ma and Silk Road recorded.

“It was a lengthy exercise for us, just trying to convey that emotional feeling that we can through the kind of instrumentation that we do. We weren't trying to emulate sounds of that era. We put trust in them as filmmakers that they could make sense of it. We trusted that they reached out to us for a reason. So we went with what we felt innately was the right thing to do.”

This is especially pertinent today, and not just because The Vietnam War is mere weeks from its debut.

Two soundtrack albums have just been announced for release: one featuring the original score by Reznor and Ross, and a second, 2-CD compilation of the  songs that appear in the program, in chronological order, songs that defined an era.

The compilation CD is remarkable because the rights alone could easily have taken years — decades, even — to gain permission for, especially on a PBS budget.

Instead, Burns and his fellow producers found that virtually without exception, every single artist they asked wanted in, as a public service. The Civil War paved the way. To everyone from Paul McCartney to Bob Dylan, whatever The Vietnam War would be, it would not be commercial, and it would not be trash.

Far from being a financial and emotional quagmire of rights negotiations and walking a budgetary tripwire, artists ranging from Bob Dylan, whose ‘A Hard Rain’s A-Gonna Fall’ sums up the opening two hours, to Paul McCartney and The Beatles, whose ’Let It Be’ is the closing anthem to the entire series, signed off without a moment’s hesitation. The Byrds, Simon and Garfunkel, The Temptations, Pete Seeger, Jimi Hendrix, Steppenwolf, B.B. King, The Rolling Stones, Buffalo Springfield, Ray Charles, The Temptations, Marvin Gaye, Cream, Crosby, Stills, Nash and Young — they’re all there, and more.

In a private conversation with TV Worth Watching, Burns said he wanted the songs for The Vietnam War  to be more than just a hit parade of ‘60s hits.

As with past Burns films, The Vietnam War takes a strictly chronological view to history. He was determined, he said, that not a single song — not one — appear in the film before the date it was actually recorded.

More importantly, Burns said — and this is key — the lyrics had to be both an accurate reflection and an integral part of what’s happening on the screen. It was not enough that ‘A Hard Rain’s A-Gonna Fall’ was both Dylan and familiar. What was important was the lyric, and how that lyric played directly into the moment Burns and Novick needed to convey —

Oh, where have you been, my blue-eyed son?

Oh, where have you been, my darling young one?

I've stumbled on the side of twelve misty mountains

I've walked and I've crawled on six crooked highways

I've stepped in the middle of seven sad forests

I've been out in front of a dozen dead oceans

I've been ten thousand miles in the mouth of a graveyard

And it's a hard, and it's a hard, it's a hard, and it's a hard

And it's a hard rain's a-gonna fall

Endings are hard. Any filmmaker worth their salt will tell you that. From the beginning, though, Burns knew there was only one song he wanted to close The Vietnam War with.

“It had to be ‘Let It Be,’” he said quietly. “It was really the only choice.”

McCartney could have been difficult, if he chose. Instead, he was quite the opposite. And so, Burns got his closing epiphany.

When I find myself in times of trouble

Mother Mary comes to me

Speaking words of wisdom

‘Let it be’

And when the broken-hearted people

Living in the world agree

There will be an answer

Let it be

For though they may be parted

There is still a chance that they will see

There will be an answer

Let it be

“It’s an invisible art,” Burns said quietly. “It’s different than just words on the page and images on the screen for us.”

Producer Botstein landed the Beatles and the Rolling Stones, and countless others, and that was “wonderful,” Burns said.

The songs work, though, only insofar as they are organic to their time.

“The thing that keeps you there, in both good and bad ways, is the emotional release you get from this extraordinary music,” Burns said. “I just felt there is something there in the heart of each of these (songs) that has an emotional connection. I don’t mean sentimental or nostalgic, but the deeply emotional connection that we always look for.”

For her part, Novick admitted The Vietnam War was a life-changing experience. The music played a large role in that.

“The question always is, what are questions that the music can help us answer?” Novick said. “When you see the film, I think you will see. We were very lucky.”

The Vietnam War premieres Sunday, Sept. 17 on PBS at 9 ET/8C, and will be repeated throughout the evening. Future segments air Sundays-through-Thursdays through Sept. 28.

The Vietnam War: Original Score by Trent Ross & Atticus Ross and The Vietnam War: The Soundtrack will be released on CD and digital download on Sept. 15.