Hans-Joachim Koellreutter (2 September 1915, Freiburg, Germany – 13 September 2005, São Paulo, Brazil) was a composer, teacher and musicologist. He lived in Brazil from 1937 and became one of the country's most influential musicians.In Brazil Koellreuter taught many prominent composers, including Heitor Villa-Lobos, Gilberto Mendes, Claudio Santoro, Camargo Guarnieri, Antonio Carlos Jobim, Denis Mandarino and many others. He brought the theory of atonal music to Brazil, creating the group "Musica Nova" and inflating the debate between the "Nationalists" and "Serialists". While the former group believed in the use of folklore material for the development of their compositions, the latter believed that the more rational approach of the European school was the path to truly contemporary works. This debate played a central role in the esthetic developments of Brazilian classical music throughout the 20th Century.