Koellreutter was born in Freiburg, Germany and lived in Brazil from 1937 onward, where he became one of the country's most influential musicians.

[1] In Brazil Koellreuter taught many prominent composers, including Gilberto Mendes, Cláudio Santoro, Antônio Carlos Jobim, Denis Mandarino, Jayme Amatnecks, among others.

[2] He brought the theory of atonal music to Brazil, creating the group "Musica Viva" and inflating the debate between the "Nationalists" and "Serialists".

This debate played a central role in the esthetic developments of Brazilian classical music throughout the 20th century.

[4][5] Koellreutter died in São Paulo, Brazil, 11 days after his 90th birthday.