On Sunday night, Portland indie folksters Blind Pilot played to a packed house at the Pearl Street ballroom in Northampton in promotion of their most recent album, Sept. 2011’s “We Are The Tide.”

Montreal Americana folk quartet The Barr Brothers, comprised of members previously of improv rock trio The Slip, provided opening duties. With an experimental country blues styling, The Barr Brothers set the tone for the evening with a modernized, almost avant-garde approach to folk.

One of the defining elements of their sound was vocalist and guitarist Brad Barr’s unique playing method wherein he would often use his right hand to pull a line of wire threaded between his guitar strings while simultaneously fretting notes with his left hand, lending an ethereal and melodic drone to the instrumental breaks.

Barr’s fantastic guitar playing and cutting baritone vocals were accompanied by brother Andrew Barr’s exotic percussion techniques, such as playing his drum kit with maracas instead of drumsticks. The experimentation came with a healthy dose of traditional hard-hitting rock-based drumming. Together with Andres Vial’s contributions on bass guitar, keys and vocals and the heavenly harp playing of Sarah Page, The Barr Brothers’ sound managed to be both layered and intimate. They ended their set with a high energy rendition of the Blind Lemon Jefferson blues classic “Lord I Just Can’t Keep From Crying.”

Soon after The Barr Brothers’ set, Blind Pilot nonchalantly strolled on stage and opened their main set with the fan favorite “Keep You Right” from their new album “We Are The Tide.” Their setlist consisted mostly of a heavy rotation of songs from their latest album. Like the group’s “3 Rounds and a Sound” tour, the band featured four accompanying musicians in addition to founding members Israel Nebeker on vocals and guitar and Ryan Dobrowski on drums.

Between these accomplished additional musicians and Blind Pilot’s clearly road-tested proficiency, their songs have an in-studio sound quality even in a live environment. This was especially impressive for lead vocalist Nebeker considering how bitter cold it was even inside the crowded ballroom – Nebeker joked halfway through the set, “This is the coldest place we’ve ever played in.”

Nebeker’s captivating singer-songwriter material was duly punctuated by his backing band, adding aural texture to the folk rock foundation of most of the songs. While most of the tunes were gentle, swaying affairs led by Nebeker’s sultry tenor voice, Dobrowski offered some driving percussive backing on songs like “Always” and the crowd-pleaser “Half Moon.”

Upright bassist Luke Ydstie also sublimely complimented Nebeker’s voice with impassioned backing harmony vocals while laying down blue-jazz basslines. Kati Claborn chimed in with harmony vocals as well on top of her folksy banjo pickings and shimmering dulcimer strums.

Three-part harmonies, mixed with the subtle but poignant addition of Dave Jorgensen’s Hammon B3 and Ian Krist’s vibraphone counterparts, made for a brilliant wall of sound most indie folk bands would be incapable of holding together.

In addition to Jorgensen’s tasteful organ work, he also played trumpet sporadically throughout the show, sometimes adding a quick, colorful countermelody in between verses and other times jolting life into the set with soulful trumpet solos backed by the rest of the band.

Blind Pilot may be centered on Nebeker’s songwriting prowess, but even live they have a knack for a tight band performance. Whether it be Nebeker’s and Ydstie’s perfectly harmonized voices or the irregular yet beautiful combined timbre of vibraphone and banjo, the sextet conjures a sonic landscape that is at once simply melodic and thoughtfully arranged.

After closing the main set with an extended version of the title track from their “We Are The Tide” record, Blind Pilot eagerly returned to play an additional unplugged encore set of three songs. First was a starkly minimal rendition of “The Bitter End” off their debut “3 Rounds and a Sound,” which began with Nebeker playing by himself and the rest of the band eventually coming in through the rest of the song.

Blind Pilot then welcomed the Barr Brothers back on stage for a joint performance of a song by deceased Americana songwriter Blaze Foley. After The Barr Brothers once again left the stage, Nebeker noted to the audience how quiet they had been the whole night, and decided to play one last song completely unplugged and without mics on the floor of the venue in the middle of the crowd.

The final song was the title track from their debut “3 Rounds and a Sound,” which had been a fervently shouted request from the audience throughout the show.

Dave Coffey can be reached at [email protected].