The large variety of his compositions includes different genres such as children's and hymns, stage and orchestral music, chamber and instrumental concertos and chamber music. Klein first visited the humanistic Gymnasium in Landau. During this time he learned to play the piano, the violin and the viola. Later he began to learn the trumpet and the organ. Very early he began to compose. As a teenager, he conducted his own works in the school orchestra on the occasion of school and commemoration ceremonies. At the age of fourteen, Klein played his own works for piano and songs in 1935 at the former radio station Kaiserslautern (1926-1945). After graduation in the war year 1940, he was drafted for military service. In 1943 he was badly wounded in fights and lost in a row a leg by amputation. He had to thereby distance himself from his actual career aspiration to become a conductor. Due to the heavy war injury he did not have to participate in the war any longer and therefore was able to study music in Trossingen from 1944. From 1946 to 1948 he continued his studies at the Musikhochschule Stuttgart. His teachers included Hans Brehme (piano), Wolfgang Fortner (composition), Hans Grischkat, Karl Münchinger and Bertil Wetzelsberger (conducting) and Philipp Mohler (composition). In 1948, Klein attained artistic maturity in conducting and composition and at the age of 27 was one of the youngest to receive a teaching assignment for composition at the Musikhochschule Stuttgart. The following year he became a lecturer in music theory at the Northwest German Music Academy in Detmold. Between 1948 and 1950, he took parallel to his teaching assignment a private study of twelve-tone technique by Wolfgang Fortner. In the period from 1960 to 1984 he taught composition, morphology, score and basso continuo playing at the Music Academy Frankfurt am Main, from 1965 as a professor. From 1985 to 1996, i.e. until his 75th year, Klein taught at Hoch's Conservatory in Frankfurt am Main. Over a period of four decades Klein was a freelance music editor for the Fidula publishing house. (Wikipedia).