Chain Reaction (1973–74): “effetto farfalla” e strumenti eolici in un’installazione performativa di Mario Bertoncini

Chain Reaction (1973–74) is both a composition and a performance-installation, designed and realized in Berlin by Mario Bertoncini in collaboration with the op-kinetic English artist Peter Sedgley. It is the first work in which the composer employs sound objects — sculptures expressly made with the purpose of vibrating through an Aeolian stimulation: a pair of “harps” and a pair of “gongs”, stimulated by adjustable compressed air or human breath. An electronic system attends both to the amplification and projection of sound, and to its conversion in coloured light: the chromatic signal is projected into a performance space, set up with grids made of reflecting/absorbing tubes, which also function as score-screens for the two performers.
The Aeolian sound material, on which the first part of the contribution focuses, in the perspective of the informel musical thought, already implies as such a reference to the sphere of the nature. Nonetheless, both the compositional and performance strategies, bound together to the intermedial layout of the work, were developed by Bertoncini in order to achieve a sort of a non-predictive sound-and-light ecosystem, lacking the necessity of a written score.
A detailed score, found in the composer’s personal archive, was initially written down, but later put aside, as it would imply a closed, deterministic model of feed-back between sound gesture and chromatic signal. The model Bertoncini then preferred is instead open, process-like, and connected to the theories of chaos that have been applied to meteorology: the two performers set their respective sound gestures live, on the basis of their tonality as well as the intensity of the perceived colour, intensity being a parameter that cannot be exactly quantized, and therefore not exactly replayed. According to Edward Lorenz’s so-called butterfly effect, an unperceivable difference of values engenders in the long term, within a multidimensional and instable system like this, even greater deviations from the foreseen trajectory. Hence, even if the starting sound gesture and the light-sound conversion code were the same, two identical performances of Chain Reaction system would be impossible.