Inching.

It's a word The Helio Sequence guitarist and vocalist Brandon Summers uses to describe the evolution of his band's sound, and it couldn't be more apt.

The Portland-based duo — which will play Bend's Tower Theatre Wednesday as part of the PDXchange Program (see “If you go") — has been one of the most remarkably consistent acts in indie rock over the past dozen years, its sonic identity shifting at a pace slightly quicker than continental drift.

That's not to say The Helio Sequence is aesthetically stagnant. To the contrary, it's a sweetly swirling synthesis of reverb-soaked electro-pop, Summers' soaring melodies and the rhythmic momentum of drummer and human metronome Benjamin Weikel. The result sounds like a narcotic dream that would drift off into the soft-glow of night if it weren't tethered to the steady clip of interstate travel.

It's been that way all along, really, but especially since 2004's “Love and Distance," an excellent album that transitioned Summers and Weikel away from the hazy textures of their first two albums to the more focused melancholic pop of 2008's “Keep Your Eyes Ahead" and last year's “Negotiations." (Each of the band's past three albums have come out on Seattle-based super-indie Subpop Records.)

“Negotiations" feels like the largest step in The Helio Sequence's shuffling journey so far. Written, rehearsed and recorded in a new practice space after an old one flooded in 2009, its 11 tracks contain even more warmth and space and echo than the band's previous work, and that's saying something. It's also no surprise; the new practice space was more quiet and isolated than its predecessor, and those qualities creeped into the record's creation.

That's natural when you make albums like Summers and Weikel make albums.

“We really do go into every record with just a blank slate, and we kinda create as we go. We don't even write a batch of songs and commit them to a record," Summers said in a recent telephone interview from a tour stop in Florida. “It truly is like write as you go and learn what the identity of the record is as you go, so in essence, every record is a fresh start for us.

“And that's both a challenge and the excitement of it," he continued. “It keeps it exciting, but there's also a lot of self-doubt (and) there are a lot of points where you feel like you're lost and you're trying to find your way through the thick of a forest, so to speak."

Summers said the flooded practice space, which happened while the duo was on tour, seemed like just an obstacle to overcome at the time. But looking back, he can see how it did lend a sense of “isolation" and “introspection" to “Negotiations."

Also affecting the record: the duo's purchase of new turntables and the vinyl rabbit hole that resulted. Summers began listening to more jazz and instrumental music. Weikel started getting into old electronic stuff.

The sound of those records was an “eye-opener," Summers said. “The thing that was in common with all this music was that it was recorded on gear that was old."

He continued: “As much as we're songwriters, we're producers and engineers, and we're interested in the technical side of things. And it's not technology for its own sake. It's always (how the technology) allows you to reach the aesthetic that you want."

The duo — gearheads from the beginning — climbed into a new “hi-fi world," Summers said, acquiring better amps and speakers and, in his words, “geeking out on cabling," all with an ear toward The Helio Sequence's one big, ever-elusive goal.

“We're always learning more and applying that to our songwriting and helping our sound," Summers said. “And I think we're just always inching closer and closer to our ideal sound.

“And the great thing is that once you think you've got it — you finish a record and you're like, 'Oh we really nailed it this time' — you give it a little bit of time and you look back and you think, 'Oh, we didn't get it here and here and here and I would like to do this (differently).' And then you take off in a completely new direction."