"During this period of concentration, I created, around 1947–1948, a monotone symphony whose theme expresses what I wished my life to be. This symphony of forty minutes duration (although that is of no importance, as one will see) consisted of one unique continuous sound, drawn out and deprived of its beginning and of its end, creating a feeling of vertigo and of aspiration outside of time. Thus even in its presence, this symphony does not exist. It exists outside of the phenomenology of time because it is neither born nor will it die, after existence. However, in the world of our possibilities of conscious perception, it is silence – audible presence."
Yves Klein, excerpt from « Overcoming the problematics of Art », 1959

"Silence … This is really my symphony and not the sounds during its performance. This silence is so marvelous because it grants happenstance and even sometimes the possibility of true happiness, if only for only a moment, for a moment whose duration is immeasurable."
Yves Klein, excerpt from « Truth becomes Reality », 1960