PHOTOS: Unexpected musical collaborations

Henry handled the musicians based in California, including Doe — who has long nurtured an appreciation for vintage folk, country and blues when he isn't busy thrashing his electric bass with X — and Chris Hillman, a founding member of the Byrds, the Flying Burrito Brothers, Stephen Stills' Manassas and the Desert Rose Band, among other groups.

Hillman chose to sing Foster's anguished "Hard Times" a song that had a significant resurgence in the pop music world in the 1980s when Bruce Springsteen, Nanci Griffith, Jennifer Warnes, James Taylor and numerous others revisited it on records or in concert.

"I'm somewhat of a Civil War buff," said Hillman, 68. "It was an unbelievable moment in the history of this country. I love history, but the Revolutionary War I'm not as up on, and it didn't resonate for me as much as the Civil War. There were so many layers of things going on. I didn't realize until about 10 years ago that [Abraham] Lincoln suspended habeas corpus and had done so many illegal things at the time. What this album does for me is it retells the story. So much of the music carries a semblance of a look back and keeps it alive."

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Keeping a bygone era alive doesn't happen without its challenges.

The Carolina Chocolate Drops, a historically astute band that has delved into 19th and early 20th century African American music since forming almost a decade ago, recorded "Day of Liberty." As written, the song includes references to "darkies," "whitey" and "massa" that presented a historical and ethical dilemma as the Chocolate Drops tackled song that joyfully anticipates the promise of freedom Lincoln and the Union Army held out for slaves.

"You don't want to sanitize it," lead singer Rhiannon Giddens said, "but you also don't want it to distract from the overall message of the song. In this case, we changed it because we didn't want the language to become the focal point. It was pretty easy because it was just a word here and a word there."

That's part of the broad spectrum of perspectives and emotions Poster set out to capture in "Divided & United."

Poster also wanted to tacitly salute many of the influential musicians who have kept this music alive through the century and a half since the Civil War, from country's pioneering Carter Family in the 1920s and '30s to the Country Gentlemen in the '50s and '60s through progressive country and roots musicians including David Grisman and the Grateful Dead. Many songs those acts recorded were among those selected for "Divided & United."

Ashley Monroe sings "Pretty Saro," the lament of a poor young man saying farewell to his love, who abandons him for a "freeholder who owns a house and land."

"With a lot of these songs you actually felt what that person was writing," said Monroe, 27. "They weren't thinking about 'This needs a bridge' or 'Where's the chorus here?' They simply, exactly expressed what they were feeling and put to a beautiful melody. Those are the ones that endure."

In some respects, songs are more revealing even than original newspaper accounts, diaries or first-person accounts of battles.

"The songs that come out of that era are the most reliable history we have," producer Henry said. "Songs are fluid the way the world is fluid. It's one thing to document events with names and dates. But it's quite another to document a time and an emotional landscape in song."

And for Henry, as with several other of the "Divided & United" participants, the modern-day relevance is clear. It's mere coincidence but hardly irrelevant that the album is surfacing so recently after partisan bickering in Washington, D.C., resulted in a partial government shutdown for 16 days.

"We're still involved in a civil war, one that feels more pronounced than at almost any time in my adult life," he said. "Sadly, it feels incredibly resonant to be revisiting in any way such a divisive time in the nation's history.

"We're not looking at it through the lens of nostalgia but through the lens of affirmation," he said. "We're not nearly evolved as a country as we advertise ourselves to be."

Updated Nov. 4 at 12:57 p.m.: This story stated that Woody Guthrie took the melody of the song “Hobo’s Lullaby” from a Civil War-era song, “Just Before the Battle, Mother.” “Hobo’s Lullaby,” which was recorded and popularized by Guthrie, was written by Goebel Reeves.