 However, this same title, only in French—"Étude sur un seul son"—had been used by Boulez for the first of his two concrète études, realised in 1951.Pierre Schaeffer, in an interview conducted many years after the fact, refers to both of these works by the same title and recalled that the tape of Stockhausen's "Study on One Sound" was only about 50 centimeters long—lasting less than one second at 76.2 cm/s..