Karlheinz Stockhausen (German pronun­cia­tion: [kaʁlˈhaɪnts ˈʃtɔkhaʊzn̩]; 22 August 1928 – 5 December 2007) was a German composer, widely acknowledged by critics as one of the most important (Barrett 1988, 45; Harvey 1975b, 705; Hopkins 1972, 33; Klein 1968, 117) but also controversial (Power 1990, 30) composers of the 20th and early 21st centuries. Another critic calls him "one of the great visionaries of 20th-century music" (Hewett 2007). He is known for his groundbreaking work in electronic music, aleatory (controlled chance) in serial composition, and musical spatialization.