Le Polytope de Cluny: The Challenges of a Reconstruction

  • Article

by Pierre Carré, musicologist

The Polytope of Cluny, a seminal work by Iannis Xenakis, is a founding performance of multimedia art. Recent research has brought it back to life, making it possible to reconstruct it in the Espace de projection at IRCAM fifty years after its premiere.

The Polytope is designed using an unconventional technological system. Six hundred flashes that form a regular, orthogonal grid are attached to a scaffolding that follows the curves of the ancient vault of the frigidarium, which rises to a height of thirteen meters. Due to their independent dynamic activation, these lasers form scintillating effects, swirls, "ponds", "rivers" or "whirlpools", which draw their inspiration from various natural manifestations dear to the composer. Three lasers are used in addition to flashes. This is one of the first artistic uses of this technology which, at the time, was still confined to research laboratories. The red, green, and blue rays are reflected by networks of mirrors (three hundred in total) fixed to the scaffolding, forming configurations that evoke nature ("anemone", "lightning", "lotus") or mathematics ("pyramid", "rosette", "Pappus", "Desargues"). The lasers are also used to sweep through the space following arbitrary trajectories by means of mobile mirrors, or are diffracted in order to form volumetric layers that Xenakis used to describe as "aurora borealis".

Polytope de Cluny, vue des flashs © Collection Famille Iannis Xenakis

The detailed coordination of all the optical equipment was only possible by completely automating the twenty-five minutes of the event using an elaborate computer control system at the cutting edge of technological innovation. A nine-track digital magnetic tape, read and interpreted in real-time by an assembly of custom-designed logic circuits, governs all the independent lighting of the six hundred flashes and the deviation of the laser rays towards the different networks of mirrors and optical devices. Concrete music recorded on a second seven-track magnetic tape, spatially distributed on the twelve loudspeakers covering the walls of the nave, responds to the luminous effects; the dynamic diffusion of sound is itself coordinated by the control tape. This technological feat makes the Polytope one of the first uses of real-time computer control for a performance of this scale.

But it is this very dependence on expensive, cutting-edge technology that, combined with the show's considerable size and technical challenges, has condemned the Polytope to remain an artistic hapax, and so since its demise in 1974 it has never been staged again. Only a few artifacts remain today—photographs, short video clips and soundtrack—that don't do justice to the immersive nature of the performance and its dynamic light processes.

Fifty years later, a research project was needed to restore the Polytope de Cluny to its full potential. The main challenge was to recreate the specifications of the installation and to retrieve the control data. However, the composer, himself not very concerned with the perpetuation of his artistic productions, left only patchy and sometimes self-contradictory documentation. In addition, few intermediate documents remain today: the compositional intentions were directly transformed with the help of a central computer into digital order data stored on magnetic media. The scarcity of sources is further exacerbated by the fact that, during the development of Polytope, informal oral exchanges between the various actors involved in the creation of the show (technicians, computer specialists, engineers, administrators, etc.) took precedence over the production of documents that can be used today. Finally, the control tape did not contain a program, but data stored in an ad hoc format that are inseparable from the electronic devices intended to read them; these have become obsolete, and the logic circuits designed for the performance have long since disappeared.

In spite of these limitations, the cross-referencing of different documentary sources has made it possible to reconstruct the genesis of the show and to determine a reconstruction of the technical set-up. This analysis, which was mainly based on the Xenakis family archive, combined documentation consisting mainly of estimates, correspondence, sketches, computer listings and technical rosters, with photographs and video excerpts that were further clarified by precious testimonies collected from several people involved in the original project.

The key to the reconstruction of the Polytope de Cluny lies in the recovery of the audio tracks and control instructions. While the audio tape storing the original music is digitally preserved in the composer's catalog, the control data was until recently considered lost. Fortunately, the original copy of the nine-track control tape was located in the audiovisual department at the BnF. This tape was then digitized on specialized equipment, which allowed the recovery of the control data. The comparison of this binary data with the reconstitution of the technical system made it possible to interpret the control instructions, the results of which were finally refined in the context of an artistic critique using computer simulations.

This research project, which makes it possible to envisage the perpetuation of the Polytope de Cluny and reopens access to a major piece of the repertoire, offers us the possibility of a full-scale reconstitution of the performance in its entirety. The piece will now be shown again at IRCAM, readapted using current technologies and to the geometry of the Espace de projection. The year 2022, which marks both the centenary of the composer's birth and the fiftieth anniversary of the premiere of Polytope, offers the opportunity to (re)discover this work, which heralded the arrival of multimedia events and performances.

Image credits : Croquis Polytope de Cluny © Collection Famille Iannis Xenakis

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