Kleiber was born in Vienna, and after studying at the Prague Conservatory, he followed the traditional route for an aspiring conductor in German-speaking countries of the time, starting as a répétiteur in an opera house and moving into conducting in increasingly senior positions.

In Berlin, Kleiber's scrupulous musicianship and enterprising programming won him a high reputation, but after the Nazi Party came to power in Germany in 1933, he resigned in protest against its oppressive policies, and left the country, basing himself and his family in Buenos Aires.

Kleiber was regarded as an outstanding conductor of Mozart, Beethoven and Richard Strauss and encouraged modern composers, including Alban Berg, whose Wozzeck he premiered.

[2] Gál pointed out that the traditional route to becoming a conductor was to start as a Korrepetitor (répétiteur) in one of the many opera houses in German-speaking countries, but Kleiber had never been taught to play the piano.

Kleiber, invited to conduct a single performance of Fidelio in August 1923, made a highly favourable impression, and three days later he was appointed to succeed Blech with a five-year contract.

Kleiber, who was not Jewish, politically active, or otherwise persona non grata with the Nazis, could have continued his career under their régime, but he would not accept their racial policies or their stifling of artistic freedom.

"[12] Prevented from performing Lulu, Kleiber made a gesture of defiance to the régime by putting the world premiere of the suite from the opera in the programme of the last concert he gave in Nazi Germany.

The New York Times reported Kleiber conducted the final opera performances to which he was contractually committed and then left Germany with his wife and children in January 1935.

In 1938, at the invitation of Sir Thomas Beecham, he appeared for the first time at Covent Garden, conducting Der Rosenkavalier with a starry cast headed by Lotte Lehmann.

[a] He repudiated his contract with La Scala, Milan in April 1939, shortly after Mussolini's fascist régime enacted its own anti-semitic legislation.

The performances he conducted featured some of the world's top singers of German opera at the time, including for example Kirsten Flagstad, Astrid Varnay, Rose Bampton, Max Lorenz, Set Svanholm, René Maison, Hans Hotter and Alexander Kipnis.

[4] The record producer John Culshaw wrote: The Covent Garden management hoped Kleiber would become the company's musical director, but he was not willing to commit himself.

At the time, hostility between the Soviet bloc and the western allies was intense, and some ardent democrats thought Kleiber wrong to work for the totalitarian East German régime.

[4] Grove comments that Kleiber's recordings of Der Rosenkavalier, Le nozze di Figaro and Beethoven's symphonies "all demonstrate his extraordinary rhythmic control and dynamic flexibility".