Low is a band that defies easy characterization. Over their 15 years as lauded pioneers of the minimalist brand of indie rock they're so closely identified with (they're not crazy about the oft-applied term "slow-core"), the husband-and-wife team of guitarist Alan Sparhawk and drummer Mimi Parker -- plus a revolving roster of bassists -- has seemed to thrive on juxtaposition. At once reflective of their faith and steeped in the violence of the human condition, Low's music is anchored by the couple's haunting vocal harmonies.

Dutch filmmaker David Kleijwegt's fascinating new documentary about the band, You May Need a Murderer, chronicles their life at home in Duluth, Minnesota, as well as on the road, touring for Low's latest record, Drums and Guns (Sub Pop, 2007). The film opens with Sparhawk dressed for church, reading the words, "Repent, for the great day of the Lord has come." He says to the camera, "The coldness of man to one another is such that, even in modernized, enlightened times, we still find justifications for going to war and killing each other." In the same breath, he says, "No matter what terrible things we do to each other as brothers and sisters, I think we still have a loving God, a parent giving us every opportunity to resolve that."

Drums and Guns covers decidedly darker terrain than most of Low's previous work, concentrating mostly on various types of warfare. Alternately preachy ("Our bodies break/ And the blood just spills and spills/ But here we sit, debating math," Parker and Sparhawk plead on "Breaker") and contemplative ("Where would you go/ If the gun fell in your hands?" asks "Sandinista"), Drums continues to move away from the group's quiet beginnings, enhancing the harsher sonic edge they began experimenting with on Things We Lost in the Fire (Kranky, 2001) and built on with The Great Destroyer (Sub Pop, 2005).

Murderer makes clear that Sparhawk, particularly, has wrestled with identity. "Where's the place of music, in its godly nature, when the lights are flashing and people are drunk and screaming?" he asks of playing in bars and clubs. "I don't know. Jesus went to the temple, but he also spent a lot of time on the edge of town." Its narrative, though, is rooted in the remarkable balancing act he and Parker, who both grew up in the same rural county -- "the poorest in Minnesota," Sparhawk points out -- are able to navigate raising two children and taking a rock band across the world. (One scene depicts the family in their living room, improvising the song "Sharp-Tooth Dinosaur.")

Parker tells a story about members of their church approaching the two after a Low show, asking them about the meaning of their titular song, "You May Need a Murderer," with its lyrics, "One more thing I'll ask you, Lord/ You may need a murderer/ Someone to do your dirty work." Sparhawk clarified, "It's about a moment when a person comes before God, asking to be a tool of God's hand, but as that tool, to be vengeful." Emphasizing the song's theme of extremism, Sparhawk says, "Nobody's listening to God anymore. And the people who say they are are liars."

Whether that answer, or the couple's vocational choice for that matter, satisfied their fellow congregants doesn't seem to concern Sparhawk too greatly. "I don't think the point of church is to gather all the good people, or the perfect people," he says in Murderer. "It's to gather those that are struggling and have the same hope."

John Potter, a former Sojourners intern, is on staff at Bread for the World. He writes about music and movies at On Tape.