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 (, 45; , 705; , 33; , 117) but also controversial (, 30) composers of the 20th and early 21st centuries. Another critic calls him "one of the great visionaries of 20th-century music" (). He is known for his groundbreaking work in electronic music, aleatory (controlled chance) in serial composition, and musical spatialization.