Hochschule für Musik und Theater München
Riedl was born in Munich in 1929 (1927 is also given as his year of birth). Following a period of studies at the Hochschule für Musik und Theater München and in courses given by Hermann Scherchen in Gravesano, Riedl, influenced by Carl Orff und Edgar Varèse, devoted himself as a composer particularly to percussion and "Lautgedichte" (sound poetry).