As a staple of Wierd Records' roster, Xeno & Oaklander displayed an admirable -- and influential -- commitment to bringing coldwave and minimal wave-inspired sounds into the 21st century. Their debut, Vigils, introduced their frostbitten analog electronics and deadpan boy-girl vocals, and from there, Liz Wendelbo and Sean McBride have found small yet significant ways to update and expand on that aesthetic with each release. Since their sophomore effort Sentinelle, they've gradually let more air and light into their music without losing any of their intensity, a move that continues with X&O's Ghostly debut Par Avion. A more streamlined missive than their final Wierd album, 2011's Sets and Lights, Par Avion maintains the aloof, challenging beauty at the heart of the duo's sound and makes it ever so slightly more accessible (much of the album was mixed by alt-rock producer extraordinaire Chris Coady). This is especially apparent on "Sheen," one of the album's standouts. Moving from a tight, almost funky beginning into more typically reflective territory, it serves as a bridge from Xeno & Oaklander's past to their future. Likewise, the synesthesia-inspired "Jasmine Nights" lives up to its sensual name with flutey synth tones that make for a striking contrast with Wendelbo's enigmatic vocals. Even the urgent duets that are a mainstay of the pair's music feel less rigidly gridded-out on Par Avion, particularly on the opening and closing tracks "Interface" and "G.Bruno," where McBride's crooning tenor -- which sounds more effortless than ever -- warm up the pristine synths, and Wendelbo assists with a breathy counterpoint. Considering that Par Avion means "by airmail," it's fitting that Xeno & Oaklander adopt an airier approach, and the album presents some of their most delicate and nuanced material alongside some of their most direct songs. "Par Avion" itself is a fascinating mix of hard-edged and ethereal, its mix of tinny beats, labyrinthine synths, and Wendelbo's wispy vocals evoking a collaboration between Adult. and Broadcast; while its meditations on memories and souvenirs don't seem catchy at first, after a few listens the song reveals itself as a stealthy earworm. At once hookier and more abstract than some of X&O's previous albums, Par Avion is another subtle step forward for the duo that should please longtime fans and win new ones.