Here, the piano is used — one could say — in a metaphorical sense. The sound is actually produced by eight Japanese gongs positioned horizontally above the mechanism of a grand piano and modulated by the extremely rapid execution of polyrhythmic figures.
The percussive, pianistic precision and the variable angle at which the hammers strike, generated through rotation, produce — thanks to the resonance of the gongs — an incessant and iridescent stream of tones.

See also: La vita di un opera