From 1952 to ’54 he studied and graduated in Rome under the guidance of Goffredo Petrassi. He attended the courses at Darmstadt from 1955 to ’62. 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.

In 1956 he met Bruno Maderna, who opened him to unknown horizons, marking a decisive turning point in his musical thought. He attended the Studio of Phonology in Milan from 1956 to ’62: this was another fundamentally important stage in his development, and it was there that he composed Collage 2 (1960), Collage 3 (Dies Irae) (1967), and Collage 4 (Jesu, meine Freude) (1979). The first performance of one of his works took place in 1947 in Wien (Poesia di Rilke, 1946) with soprano Lydia Stix and pianist Erik Werba.

The first important performance of a Clementi’s piece — after the completion of his studies in composition — was Cantata, set to a fragment by Calderón de la Barca (1954), broadcasted by the Hamburg Radio in 1956 as part of the cycle Das neue Werk.

In 1959 he won the second prize in the ISCM competition with Episodi (1958) and in 1963 he was awarded first prize in the same competition for Sette scene da “Collage” (1961).

In 1961 Collage, a work based on visual material by Achille Perilli, was presented at the Accademia Filarmonica Romana in Rome.

His opera Interludi — Musica per il Mito di Eco e Narciso was staged in 1992 during the Orestiadi Festival in Gibellina and won the 1992 Abbiati Prize.

The Scala Theatre commissioned him a new opera, arillon.

From 1971 to ’92 he taught music theory at the University of Bologna (DAMS). Clementi is often invited to give lectures and composition courses.

During the year 2005 numerous monographic concerts have celebrated the composer’s eightieth birthday; in particular, the University of Catania (Università degli Studi) has organized an international conference on Clementi’s music, on which occasion the composer has been conferred with the laurea honoris causa; during the Festival Pontino di Musica (Latina) the Incontri Internazionali di Musica Contemporanea (International conference of Contemporary Music) have dedicated to him two monographic concerts, a round table and a retrospective exhibition of his graphic work, the first up to date. During the Festival Suoni e Colori in Toscana (Rignano sull’Arno, Firenze) the composer has been awarded the prize Presidente della Repubblica. He also has received the DAMS Special Prize for his career from the University of Bologna.