LOS ANGELES — On their previous Folk Implosion albums, it was hard to tell where John Davis ended and Lou Barlow began.

But for the upcoming One Part Lullaby, the dub-pop duo said they deliberately took more defined roles. Before, they shared vocal and guitar duties. But their third studio album, due Sept. 7, finds Barlow assuming more lead vocals, while Davis zeroes in on his guitar work.

The result, according to Barlow, is their most focused and emotional work to date.

"[It's] more rich and textured-sounding, and I think ... [my] taking more of a lead vocal approach ... gets at the emotional parts of the songs," Barlow said, speaking from a Los Angeles hotel room.

"When you have a singular vocal, it's easier to get at more rocky, emotional territory," added Barlow, who also leads the rock band Sebadoh. "It was easier to express a lot of themes that seem to match the music" (RealAudio excerpt of interview).

A testament to that is "Merry Go Down," which sounds almost as if it were recorded in concert, but actually came from a four-track demo session. Barlow said the push-and-pull of the song's chorus reminded him of "that dizzy feeling after you take a ride at the fair."

"I kind of equated it to being attracted to someone or in love ... like having a crush on someone and being drug behind it."

Even though Davis and Barlow mostly divided their duties this time around, their roles did overlap on occasion — such as collaborating on the lyrics for "Free to Go." Opening with the words "Catching butterflies, line drives, watching TV," the percussive pop tune comes across as a vivid yet fragmented childhood memory.

"It was sort of fun to toss around childhood lyrics and go, 'Did that happen to you?' " said Davis, who is also a solo artist, having most recently released the album Blue Mountains (1997). "It ended up being a pretty good contrast to the diffused feelings on the record. I like how literal it is"

(RealAudio excerpt of interview).

"Yeah, there's moments to that song where it's just [so direct] — like sitting in the back seat with your sister and sticking your hand out the window and letting your hand ride on the wind," Barlow added, referring to the lyrics "Stay on your side/ My hand out the window/ Feeling the wind brush by."

One Part Lullaby recalls the rhythmic depth of Folk Implosion's work on the soundtrack to the 1995 movie "Kids," which spawned the unexpected top-40 hit "Natural One" (RealAudio excerpt). Although the two partners continue to merge hip-hop beats and samples with pop melodies, they emphasize a more layered guitar sound on the new album.

Both the opening track, "My Ritual" (RealAudio excerpt), and the instrumental "Serge" originated from samples. The former's languid vocals, laid over a wave of hypnotic drum loops, merge into a melodic chorus; the latter features frog sounds pulled from a wildlife album. "We just started putting guitar parts on it, and layering stuff over that, and then we discovered there was a song there," Barlow said.

Barlow and Davis, who have been working together on and off for more than five years, made their debut as the Folk Implosion with the 1994 album Take a Look Inside the Folk Implosion. They followed that with their The Folk Implosion EP (1996), the "Kids" soundtrack and 1997's Dare to Be Surprised.

Though Folk Implosion have toured once before, the duo said they have no plans to support Lullaby on the road, partly because they can't imagine how they'd present the songs live.

"We're stumped on that one, to be honest," Davis said. "We really dug a hole for ourselves this time."

Since both are busy with other projects, they don't waste time when they get together as the Folk Implosion. "There's no pointless jamming," Davis said, adding that most of their songs begin spontaneously, though the process rarely stays that simple. "I think it's really a combination of spontaneity and slavery," he said, citing "My Ritual," which required a 12-hour day to nail the guitar parts (RealAudio excerpt of interview).

"Always at the genesis it's definitely, totally spontaneous," Barlow agreed. "And then it's a matter of trying to maintain that spirit" (RealAudio excerpt of interview).