A mesmerizing close up on thousands of faces expressing the same feeling, thousands of souls attracted to the same emotion, the enchantment of watching a racer in slow motion as he slips away with every step or grass that in accelerated motion turns into an oak, images that the eye is unable to fix, regardless of being large or close up, long or transient. This is the essence of the mystery of cinematography, the secret of this hypnotic machine: new knowledge, a new love, a new acquisition for the eyes. (…) In improving sound film, it seemed clearly necessary to experiment with what slow motion could offer, which in fact continues to provide the world of sight with many things as of yet unseen. I asked a sound engineer about this problem from a technical point of view. Léon Vareille took an interest in it and resolved the problem with a simple and elegant solution, as mathematicians are fond of saying. Throughout Le Tempestaire, I could use the sounds of wind and sea re-recorded and with variable speeds, reaching a speed of one to four. (…) The ear needs a magnifying glass that magnifies sound over time, that is, that slows down sound, in order to hear, for example, that the dull and chaotic screaming sound of a storm breaks down into a miniature world of sounds strikingly different from one another, as of yet unheard: a whirlwind of howls, billing and cooing, rumbling, cackling, explosions, timbre and accents thatfor the most part do not even have a name. We could take an even less complicated example: the sound of a door that we open and close. Slowed down, this simple and ordinary sound reveals its complex nature, its particularities and its dramatic, comic, poetic or musical potential.

Jean Epstein, Le ralenti du son, in “Livre d’or du cinéma français”, 1947-1948