Hans-Joachim Roedelius and Dieter Moebius played a pioneering role in the evolution of contemporary electronica, first as Kluster (with Conrad Schnitzler) and subsequently as the duo Cluster. Between Klopfzeichen (1970) and Sowiesoso (1976), via the Harmonia collaboration with Michael Rother, their work offered blueprints to later artists exploring electronic music's myriad possibilities. On Cluster's first studio release in 15 years, Roedelius and Moebius send 17 sound postcards from an exotic retro-futurist world. Although that aesthetic might seem outdated, paradoxically, it never goes out of fashion. The clunky, whimsical, space-age future envisioned from the '50s onwards didn't actually become a reality, so it remains charmingly abstract and elusive -- much like Qua's impenetrable track titles themselves, which appear to be in a language spoken by androids. Mixing minute-long fragments and more expansive pieces, Qua conjures imaginary cinematic sequences in both spartan monochrome and rich Technicolor, spanning diverse moods: from the austere, droning "Xanesra" and the somber, hymnal "Flutful" to the playful "Albtrec Com" and "So Ney," which could be, respectively, cocktail jazz and calypso reverse-engineered by aliens. While this material generally loops and drifts, in places its rhythmic elements also establish a stronger structuring core and a more purposeful sense of linear momentum -- on "Malturi Sa" and "Na Ernel," for instance, tracks recalling the minimalist, beat-driven sensibility of 1974's Zuckerzeit. Roedelius and Moebius have always delighted in the studio as an instrument in itself, and they happily incorporate the accidents that environment and its tools throw up. The looped creaking of a door on "Putoil" typifies this, also underscoring a playful tension between the soundscape's fanciful futuristic world and the earthbound here and now. Notwithstanding Cluster's enormous influence on modern electronic music, it doesn't automatically follow that, in 2009 (with the pair's combined ages totaling 140), they might still have anything relevant or credible to contribute. Qua proves that they do.