Terrific nine-CD box (digipack CD sleeves!) at a fantastic price! The heart of Ligeti's output, and the basis for the consensus that places him among the 20th Century's most important composers, is the series of masterworks written during his middle period, which lasted from roughly 1957 (after his escape from Hungary) to 1977 (marked by the completion of his opera Le Grand Macabre). The "sound surface" compositions from the period, including Atmosphères, the Requiem, Lux Aeterna and much of the Second String Quartet, fall into a genre of acoustic music that was not unique to Ligeti -- it's also associated with Penderecki and Xenakis, and more peripherally with composers like Lutoslawski -- but Ligeti was arguably the greatest of the lot. Central to this musical language is the elevation of timbre as the most important musical parameter, supplanting the traditional pitch-priority that had been dominant in Western art music since its inception. Ligeti's vocabulary in these works consists largely of tone clusters, either in sustained notes, or as the unfolding of many rapidly moving chromatically undulating lines, in both cases creating a composite texture where the primary impression is of the resulting tone color, rather than the melodic or harmonic implications of any individual instrumental line. It is this music that came to wider attention through its use by Kubrick in the monolith and stargate sequences in 2001: A Space Odyssey. It was often called "space music" by people who picked up on that particular association.