There was a costume change, a symbolic switch from black and gloomy to bright, all-white ensembles. The musical gear got moved around a bit, too, with synthesizers and electronic beat-making devices brought out for the second half.

Mostly, though, the changeover from Death Cab for Cutie's set to the Postal Service's performance happened seamlessly and rather playfully Sunday night at the Armory.

Ben Gibbard, the singer in both bands, pulled double duty in front of a sold-out crowd celebrating the 20th anniversary of two of the biggest albums of his career. Both performances really felt like celebrations, too, even though one of the records is as downbeat and mopey as Gibbard has ever gotten.

"Thanks for coming out. We present to you, 'Transatlanticism,'" the singer, 47, said near the start of the Death Cab portion of the concert.

About an hour later, he similarly announced the beginning of the Postal Service's lone record, "Give Up." He didn't do much talking beyond that, and instead breezed through the albums like a human CD player (devices still widely in use in 2003; oh how quickly things would change).

While Death Cab remains Gibbard's main vehicle and a top-drawing rock act — the band just performed here in July at Target Field for the TC Summer Fest with the Killers — Gibbard's little side project the Postal Service was the main attraction on this twofer tour.

The group did only a brief tour in 2003 and a short 10th anniversary trek in 2013 but otherwise hasn't recorded or performed again, despite the fact that "Give Up" went platinum and remains an influential and cult-loved electro-pop album.

With beloved Americana rocker Jenny Lewis in tow as a co-vocalist and multi-instrumentalist — her cool presence is always a brightener, even when not dressed in white — Gibbard and his Postal Service collaborator Jimmy "Dntel" Tamborello did an admirable if not totally successful job recreating the electronics-heavy studio recordings on stage.

The poppy hit single "Such Great Heights" sounded a little disjointed and forced; which could also be said of Gibbard's dancing in it. Some of the album's darker or more dramatic tracks came off even stronger in concert, though, including the movie-set epic "Clark Gable" and especially "This Place Is a Prison."

Both those songs ended with Gibbard seated behind a drum kit adding extra oomph to the loopy beats. As if he wasn't already filling enough job roles on this night.

The Death Cab portion of the concert challenged Gibbard as a singer. After the high-charging opening tune "The New Year" — one the band still plays at most shows — he had to sing like a lovelorn, bright-eyed 27-year-old again in the tender second song "Lightness." He especially stepped up and delivered on vocals in the second half/side for the album's title track and centerpiece, which built up slowly and beautifully to become the emotional high point of the night.

Coming so soon after Gibbard's crew showed off their more recent fare to great effect at Target Field, some of the "Transatlanticism" tunes sounded a tad simplistic and dated. Death Cab is a group that has pretty consistently evolved over the past two decades.

Still, "Transatlanticism" captured a pivotal boy-to-man moment in Gibbard's songwriting as he grappled with long-distance love and tensions within the band. It was a treat for the many diehard fans among the 8,000 attendees to hear the more headphone-ready, late-night-listening tracks such as "We Looked Like Giants" and the longing ballad "Tiny Vessels."

Gibbard himself seemed happy to dust off "Death of an Interior Decorator," calling it his favorite on the album. "I don't know why," he added, "maybe I just like the deep cuts."

A couple familiar favorites were enlisted for a hybrid encore featuring members of both bands. First came a reprisal of "Such Great Heights," this one an acoustic duet by Gibbard and Lewis. Then, the whole crew teamed up for a lushly orchestrated version of Depeche Mode's "Enjoy the Silence."

The audience might have enjoyed hearing another Death Cab tune or two more than the cover song, but Gibbard had already done more than enough to treat the fans to something special.