For the 46 minutes of the seven-track tape of La Legende d’Eer (whose title was inspired by Plato’s Republic) Xenakis used the following families of sounds:
1. Instrumental sounds coming from Japaneseand African instruments
2. “Concrete” sounds, such as scraping on cardboard or the clash of bricks
3. Sounds computed and generated by mathematical functions (probabilities)
According to notes apparently written by Cornelia Colyer, Xenakis’s assistant for computer programming during this period, the computed sounds were written on digital tape in numerical form, then converted into sound by a 16-bit D/A converter at the CEMAMu laboratory in Paris. The resulting sounds were mixed together, track by track, in the Electronische Music Studio at
the WDR, Cologne (Collection famille Xenakis).
Concerning the spatialization of La Legende d’Eer, Xenakis makes a brief reference:
The music is on a tape of seven tracks. Each track is distributed over eleven high-quality loudspeakers spread under the shell of Diatope. The distribution, static or kinematic, is realized by a special computer program. Here the sound’s diffusion apparently followed the principles described in the 1958 article “Notes
pour un ‘geste electronique,’” where Xenakis (1971, pp. 143–150) explained the notions of static and kinematic stereophony in an electroacoustic piece.
In static stereophony, each track plays over a specific loudspeaker and the spatial effect is produced by the simultaneous performance of all the tracks. On the other hand, kinematic stereophony is made up of gradual fade-outs and fade-ins of each track as it moves from one loudspeaker to the other, having constant or varying speed. Here the spatial effect is produced by the movement of the sound of each track.
This use of complex sound movements, in addition to the piece’s duration (at 46 minutes, unusually long for Xenakis) and the requirements of the light show, demanded computer automation.
This was partially practiced by Xenakis in his earlier polytopes.
