Justified,” the Peabody Award-winning FX drama, sports an earthy musical style as distinctive as its hard-edged plots, thanks to music supervisor Greg Sill.

Over the course of two seasons, the show – which stars Timothy Olyphant as Waylan Givens, a U.S. Marshal grappling with murderous clans in the backwoods of his hometown of Harlan, Kentucky – has developed a unique, and uniquely integrated, sound of its own.

“It’s Americana, without a doubt,” Sill says.

Sill – whose music supervision credits include work on such series as “Cane,” “American Dreams,” “Friends” and “ER” – says the show’s musical style evolved year to year.

“The first season, the editors had a tendency to use country and western music,” Sill explains. “People started to fall in love with that style of music. I said, ‘Look, guys, we’re not in Tennessee. We’re in Kentucky, and once you cross the border the music changes.’ We had knock-down, drag-out arguments, seriously.”

Season one’s approach resulted in some strikingly deployed cues – most prominently, a cover of Tammy Wynette’s “Stand By Your Man” by L.A.-based vocalist Quincy Coleman, recorded by “Justified” composer Steve Porcaro. But Sill thought a shift was in order.

“I went and talked to the writers,” Sill recalls. “I had looked around to see who had the biggest amount and the biggest variety of bluegrass music and rock ‘n’ roll and rootsy stuff – ballsy music, stuff that made sense for the show…I said, ‘Let’s try to use as much roots stuff as we can.'”

An early-season, on-camera appearance in a barroom scene by veteran L.A. roots rocker Dave Alvin established the season’s musical style.

“Dave fell in love with the show, and he actually wrote a song, ‘Harlan County Line,'” Sill says. “That was the song we wound up using. We’d already picked a song of his, called ‘Out of Control.’ (Show creator) Graham (Yost) is a huge fan of Dave Alvin – that’s like his favorite guy. Dave sent me ‘Harlan’ and said, ‘What do you think?’ I flipped out. I sent it to Graham, and he flipped out. We actually integrated the song into the story. It worked really well.”

Alvin’s stint set the tone for the rest of the year. The soundtrack for “Justified” employed music by a host of Americana artists, including Gillian Welch, the Drive-By Truckers, Amelia White, Justin Townes Earle, Cliff Wagner, Lynda Kay and Jesse Dayton & Brennen Leigh.

One lesser-known act actually used their “Justified” fandom as a gateway into the show’s soundtrack.

“The producers went down to Harlan,” Sill remembers, “and this band, the Cumberland River Band, was so enamored with the show that they had written a song called ‘Justified.’ They played it for the producers, and Graham said, ‘Look, we’ve got to put some of your stuff on the show.’ I wound up putting like nine of their songs in the show.”

Sill takes no credit for one potent musical moment in season two: a rousing performance of “High On a Mountaintop” by Emmy-nominated actress Margo Martindale, who played hillbilly matriarch Mags Bennett.

“It was Margo’s idea,” says Sill. “She wanted to sing. It’s a public domain song that Marty Stuart wrote the lyrics to. She had heard the song, and read the script, and she said, ‘This is the song we should use.’ Tony Goldwyn directed the episode, and he called me and said, ‘I’d like to do it live.’ I said, ‘Are you crazy?’ She sang it live, and it was spot-on. We used her live version as the playback.”

Sill says the highest compliment paid to his work on the show came from writer Elmore Leonard, whose short story “Fire in the Hole” inspired “Justified.”

“He actually called me and congratulated me,” Sill says with a smile. “He said, ‘Listen, man, I never actually knew what music supervisors did.’ He thanked me. Very cool.”