He began his piano studies at the age of thirteen, and received his diploma in 1946 under the guidance of Giovanna Ferro, a student of Alfredo Casella. In 1947, Clementi attended Pietro Scarpini's piano master-class in Siena. In 1941, at the age of sixteen he started studying composition in Catania, where he later became a pupil of Alfredo Sangiorgi (a student of Arnold Schoenberg in Vienna in 1922-1923), who introduced him to the technique of twelve-tone composition (Catania-Bolzano 1945-1952). From 1952 to 1954 he studied and graduated in Rome under the guidance of Goffredo Petrassi. He attended the courses at Darmstadt from 1955 to 1962. His compositions Tre Studi for chamber orchestra (1956-57), Composizione n.1 for piano (1957) and Triplum (1960) were performed here for the first time.