His music education continued under distinguished teachers at the Vienna Hochschule für Musik,[2][3][4] which he never attended formally, and from which he did not obtain any degrees.

When the war broke out, however, he volunteered for the army and also became an active revolutionary: in 1918 he joined the circle of left-oriented intellectuals in Vienna who recognized his artistic talent.

He already had several works ready; he recited the poem Vigilia to his colleagues, and he was sixteen when the Tonkünstlerorchester of the Vienna Musikverein conducted by Bernhard Paumgartner premiered his Fantasy for the Orchestra.

Not many of Matačić's compositions have been completely preserved, although he did include some of them in his programs after becoming a distinguished conductor – such as the Confrontation Symphony or the Konjuh planina Cantata.

Until 1954, when he managed to get an approval from Tito to be issued a passport, his activities in the former country were limited to Rijeka and Ljubljana, but soon his career gained full international momentum.

The recording in 1954 of highlights from Richard Strauss's Arabella (with Elisabeth Schwarzkopf) in London for the Columbia label marked a new beginning in the conductor's life.

The following year he replaced Karl Böhm at the Bavarian State Opera in Munich for a triumphal performance of Strauss's Ariadne on Naxos.

Appearances in Berlin, Stuttgart, Augsburg, Salzburg, Graz and elsewhere followed, where he conducted concert programs, operas, and often even directed the productions.

The musicians he collaborated with include Sviatoslav Richter, Arthur Rubinstein, Christian Ferras, Rudolf Buchbinder, Marijana Radev, Ruža Pospiš Baldani, Elisabeth Schwarzkopf, Christa Ludwig, Renata Tebaldi, Birgit Nilsson, Leontyne Price, Nicolai Gedda, and Dietrich Fischer-Dieskau.

His first appearances with the Berlin Philharmonic Orchestra in 1936 already included a suite from Krešimir Baranović's ballet Gingerbread Heart and Jakov Gotovac's Symphonic Kolo.

It deals with the threat of destruction by nuclear weapons in a harsh musical language that includes quotes from the "Dies Irae" Theme from Hector Berlioz' Symphonie Fantastique.