Karlheinz Stockhausen was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th and early 21st centuries. He is known for his groundbreaking work in electronic music, having been called the "father of electronic music", for introducing controlled chance into serial composition, and for musical spatialization. He was educated at the Hochschule für Musik Köln and the University of Cologne, later studying with Olivier Messiaen in Paris and with Werner Meyer-Eppler at the University of Bonn. As one of the leading figures of the Darmstadt School, his compositions and theories were and remain widely influential, not only on composers of art music, but also on jazz and popular music. His works, composed over a period of nearly sixty years, eschew traditional forms. In addition to electronic music-both with and without live performers-they range from miniatures for musical boxes through works for solo instruments, songs, chamber music, choral and orchestral music, to a cycle of seven full-length operas. His theoretical and other writings comprise ten large volumes.