Although identical twin sisters Tegan and Sara Quin first appeared in the music scene in the late '90s playing the kind of folk-rock and folk-punk more associated with other Lilith Fair (in which they participated) artists of the time, by the time 2007 rolled around they had moved into much poppier territory.

It was a progression, to be sure, from This Business of Art to their fourth Vapor full-length -- one that can be heard in the time spent on production, the louder guitars -- but that still may not prepare listeners for The Con.

Produced by Death Cab for Cutie's Chris Walla, the album is full of quirky, Aqueduct-like keyboards, punchy bass from Weezer's Matt Sharp and AFI's Hunter Burgan, and even some guitar help from Kaki King that stretch and shove their way into the spaces between Tegan and Sara's hook-driven melodies and clean harmonies, more complex than anything they've done before.

Though each sister writes and sings lead on seven tracks, it is Sara especially who writes the more intricate pieces ("Relief Next to Me," "Like O, Like H"), showing a more adult songwriter, one who has matured since her first work came out, while Tegan draws more from simpler emo and pop-punk arrangements ("Nineteen," "Hop a Plane"), her songs more straightforward, both compositionally and lyrically, than her sister's.

But this isn't to say that there's a kind of disparity or harsh contrast on The Con.

Much like the duo's voices, which share a timbre, a clear relationship, even if their actual tonality differs, the songs on the album complement each other, play off the other's strengths, and make the record very much an entity instead of simply a collection of tracks, setting it off as an impressive step forward in their already commendable discography.