Argentine composer Mauricio Kagel (1931-2008) made his reputation in the 1950s through his association with composers in the "Darmstadt School," though his music isn't like that of Stockhausen or others associated with it. Fascinated with arcane instruments and collage, Kagel fashioned pieces such as Heterophonie (1961), Musik für Renaissance Instrumente (1966), 1898 (1973), and Rrrrrrrr (1981), which are musical universes unto themselves, yet referential to outside influences. Late in life, Kagel became a significant, if controversial, figure in European opera; Kagel once stated that "An essential aspect of my work is strict composition with elements which are not themselves pure."