At the turn of the 19th and 20th centuries, two theatres were situated in the Opera House, built in 1892: German Theatre, which later moved to the today's Drama Theatre and Slovenian Provincial Theatre, which boasted both drama and opera ensembles - conductors, soloists and choir, engaged on a permanent basis. Until 1908, when the Slovenian Philharmonic Orchestra was established, opera performances were accompanied by bandsmen of the 17th (Carniolan) and 27th (Styrian) Infantry Regiment of the Imperial and Royal Army. From 1908 to 1918, opera performances were accompanied by the Slovenian Philharmonic Orchestra.
The theatre was organised again by the all-national Slovenian Theatre Consortium in the last year of WWI. The members of the Directory of the Slovenian Theatre Consortium were mainly the representatives of politics and capital, whereas the cultural workers, such as Anton Funtek, Matej Hubad, Fran Saleški Finžgar, Alojz Kraigher, Oton Župančič and Izidor Cankar, were represented in the Theatre Council. Amongst the most deserving for the theatre’s renovation was Fran Govekar who organised Slovenian Ballet and Opera. He gathered the technical staff, singers, orchestra, choir and conductors. A few months after the end of the World War I, both Drama and Opera Theatre operated together in the today's Opera House in Ljubljana, under the auspices of the new National Theatre, which was renamed later, in the 1919/1920 season, Slovenian Royal Theatre and in 1920, following the nationalisation, National Theatre again. The Drama Theatre moved to its own stage and permanent premises in the beginning of 1919.
The professional Opera Orchestra, consisting of 54 musicians, was established in 1918. It performed mainly Italian and French operas, also placing particular emphasis on Slavic and Slovenian operatic works. Since 1918, when the professional Ballet Ensemble was established as well, the orchestra accompanied both classical and newer ballet creations.
While the ensemble of the Drama Theatre restored its Slovenian theatre performances in the Ljubljana SNT Opera and Ballet hall, where only films were showed to the audiences during the war, already in the beginning of the 1918/1919 season and staged on 29th October as the first performance of the drama theatre Finžgar's play Wild Hunter, the first opera performance, presented in the renovated National Theatre, was The Bartered Bride by Bedřich Smetana, in December 1918.