Metastaseis is widely considered Iannis Xenakis' first mature work. It is also one of just a few pieces, like Beethoven's Symphony No. 9 and Stravinsky's Le Sacre du Printemps, that irrevocably changed history. Metastaseis treats the orchestra as if it were material for architectural construction. (Xenakis was working at the time for famed architect, Le Corbusier.) The textures, featuring the orchestral strings, are shaped according to global concerns and proportions rather than motivic development or contrapuntal combinations. Never before had the sliding sounds of the glissando been treated as a primary element; never before had each player been required to play an independent part, the 46 glissandi interlocking to create textures of incredible intensity and dynamism. For the audience at its first performance at the 1955 Donaueschingen Festival in Germany, it was as if this composer had arrived from another planet (to paraphrase one critic); the cheering and booing carried on far longer than the piece itself.
The opening of Metastaseis has come to seem archetypal. The full complement of strings enter in succession, sustaining a single note. Gradually, individuals pull away, sliding slowly toward new notes. The listener, whose ear has been drawn into the rich inner energy of this opening unison, finds the sound expanding in continuous fashion, with no points of stability along the way for orientation. Eventually, the texture fills out the full range of the strings, arriving on a massive cluster of 46 notes. This sonority, also never heard before in the history of music, carries on, being articulated by changes of dynamics and mode of playing, the durations governed by the Fibonacci series (1, 2, 3, 5, 8, 13, etc.), which, coincidentally, is closely related to Le Corbusier's modular proportions.
The second section is more "traditional." Most of the orchestra drops away, leaving a group of strings playing an angular, contrapuntal passage that is strongly reminiscent of Webern and his serialist successors. In a sense, this section makes explicit how far removed the rest of the score is from the concerns of other composers. This section is followed by a third, in which the global glissando texture of the opening is fragmented, creating a succession of short gestures, usually fanning out from a single pitch. The winds and percussion have a more prominent role here, too, though always subjugated to the strings. Metastaseis closes with a shortened version of the opening, reversed so that the strings, beginning on a large cluster, gradually close in on a single mid-register unison. At the end, it's apparent that Xenakis has taken us on an incredible journey, voyaging through sonorities strange and new, bursting with energy but carefully organized.