There's a glitch in "Stranger Maker," a song from Ah Holly Fam'ly's new album Reservoir. At their sleepy Thursday night rehearsal in outer Northeast, the eight-piece breeze through a set of orchestral folk they're prepping for the next day's show. That is, until the discovery of a very un-Fam'ly-like resonance in this newish song. Frontman Jeremy Faulkner suggests they sweeten the harmony. Flutist Alexi Erenkov diagnoses the problem more precisely in music theory terms that put half the room at ease—and soar over my head.

The mix of intuition and analysis the band use to get "Stranger Maker" back on its feet sounds like several different languages being spoken in one conversation. It's as if I stepped out of the cozy living room that greeted me an hour earlier and walked into a summit of Tascam dreamers and classically trained boffins.

Faulkner is the reluctant leader of this clan. Along with his whisper of a singing voice, Ah Holly Fam'ly's sound includes the voices of Becky Dawson (who is married to Faulkner) and Amelia Harnas; cello and bass from Jeff Diteman; Whitney Menzel's drums; and varied strings and woodwinds contributed by Erenkov, Morgan Hobart, and Jared Arave. Everyone composes for their own instrument. But it was Faulkner's private songbook, written throughout his teens in Idaho that in 2003 led to a spate of local shows in the college town of Moscow.

Just as Leonard Cohen's lyrics attracted Faulkner to songwriting, Faulkner's own words inspired his collaborators to join him. "Lyrics are always very important to me, and Jeremy always wrote great words," Diteman says. He was one of the group's founding members, back when they played under puckish variations on the name "The Holy Family" (Ah Holly Fam'ly is where this game wound up). Once they moved to Portland, the current lineup fell quickly into place. The way Harnas went from friend of the group to a member is typical of the casual yet resolute way people enter their fold. "Before I was in the band, when I only lived in the house," Harnas says, "I would sing harmony in the bathroom above the practice space."

Such timidity is a recurring theme in the group's story. From the name games of the early days to their initial reluctance to move to an indie rock mecca, Ah Holly Fam'ly have insulated themselves from the hype that can stunt a band's musical growth.

The prize for this self-preservation is Reservoir, their exceptionally fine-hewed second album. Here, they augment New Weird America with old European chamber music. Their sound is poised and ghostly—like a dilapidated house resting on a solid foundation of sudden tempo changes. By combining the stately and the strange, Ah Holly Fam'ly turn Reservoir into an extension of the group's core indie-folk influences.

Back to rehearsal and "Stranger Maker." Harnas asks the summit, "So the cello, violin, and flute are playing the same note?" It's true. Somehow, the harmonics of three middle A's stacked atop each other isn't very Fam'ly. Then, in the way spunky computer hackers do it in the movies, right after they've dropped a mouthful of technical jargon, Erenkov offers a pithy solution: "Someone's gonna have to play a different note."