Gustav Mahler was one of the many conductors who have worked in Vienna. During his tenure, Mahler cultivated a new generation of singers, such as Anna Bahr-Mildenburg and Selma Kurz, and recruited a stage designer who replaced the lavish historical stage decors with sparse stage scenery corresponding to modernistic, Jugendstil tastes. Mahler also introduced the practice of dimming the lighting in the theatre during performances, which was initially not appreciated by the audience. However, Mahler's reforms were maintained by his successors.
Herbert von Karajan introduced the practice of performing operas exclusively in their original language during his directorship of the company; prior to this, operas were performed in German. He also strengthened the ensemble and regular principal singers and introduced the policy of predominantly engaging guest singers; and began a collaboration with La Scala in Milan, in which both productions and orchestrations were shared. This created an opening for the prominent members of the Viennese ensemble to appear in Milan, especially to perform works by Wolfgang Amadeus Mozart and Richard Strauss.
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