The 1980s, a decade synonymous with hair metal and overwrought power ballads, weren’t exactly a high-water mark for experimental rock. But, in 1984 and 1987, the Belgian ensemble Univers Zero released two albums that were among the best of an avant-garde scene that defied the cheesiness of the era. Uzed and Heatwave explored electro-acoustic chamber music, with bandleader and primary composer Daniel Denis combining Bartók-ian gloom with dissonant guitar solos and insistent rhythms. Relaps, a new release from Silver Spring’s Cuneiform, is the only live document of Univers Zero’s Uzed/Heatwave period, during which time the group played only nine concerts. Still, the quality and intensity of the performances on Relaps indicate a remarkably practiced band. Virtually all of Denis’ pieces from Uzed are included on the disc, along with the two major compositions from Heatwave, both of which were written by the band’s keyboardist, Andy Kirk. While the studio recordings were marred by tinny, dated production, the sound here is excellent—or at least as good as can be expected of 20-year-old tapes. As befits the band’s penchant for atmospherics, the two longest selections are also the most effective. The harrowing “Emanations” vacillates between quiet, stark passages and a dark intensity evident in the brief, clawing guitar solo that brings the piece to an epic and somber conclusion. “The Funeral Plain,” a sprawling 20-minute composition, is the centerpiece of Relaps. An almost Romantic-era symphonic sweep makes an odd appearance about halfway through, but otherwise the piece’s chamber-ensemble feel is unmolested. The last few minutes of the piece consist of an enthralling buildup, as a violin and clarinet share a propulsive theme, over which Michel Delory spews molten, Hendrix-like spasms of electric guitar. Meanwhile, Denis is clearly in control throughout, his stickwork too complex to scan neatly as rock drumming or classical percussion. It’s a good reminder that Univers Zero was far ahead of its time, even if it was (and remains) lost between serious and popular music.