The Zagreb Philharmonic Orchestra (in Croatian Zagrebačka filharmonija) -- whose foundation marked the beginning of large-scale orchestral music-making in what is now Croatia -- is one of the oldest symphonic ensembles in the Balkans. It continues to attract top-notch international stars as guest conductors. The modern Zagreb Philharmonic emerged from the orchestra of the Croatian National Theater in the middle of the 19th century. At the time, concerts of independent orchestral music were rare and were mostly amateur affairs, but greater professionalization began when the Zagreb Opera was founded in 1870. The following year, the composer Ivan Zajc began to organize instrumental concerts, devoted at first to performances of popular operatic tunes and later to independent orchestral compositions, Croatian and otherwise. Zajc termed these events Quodlibet concerts. Full-scale symphonic concerts became more frequent in the years before World War I, and after the war's end, a Philharmonic of the Theater Orchestra was reestablished. In 1920, it took the Zagreb Philharmonic Orchestra name. The orchestra's principal conductors have included Friedrich Zaun, Milan Horvat, Lovro von Matačić, Mladen Bašić, Pavle Dešpalj, Kazushi Òno, Pavel Kogan, Aleksander Rahbari, Vjekoslav Šutej, and, at present, David Danzmayr. Dimitri Kitaenko is the current artistic advisor. The orchestra's guest conductor rosters over the decades reads like a who's who of Central and Eastern European conducting, including Valery Gergiev, Antoni Wit, Kirill Kondrashin, Bruno Walter, Paul Kletzki, and Kurt Sanderling, as well as Leopold Stokowski, Sir Malcolm Sargent, Jean Martinon, and Sir Neville Marriner. The orchestra has mounted ambitious concerts such as a 2012 performance of the Mahler Symphony No. 8 ("Symphony of a Thousand"), for which the group teamed with the Slovenian Philharmonic Orchestra. An unusual feature of the group's public interface is a series of orchestral open houses called Doors-Open Day. The Zagreb Philharmonic was signed to Germany's prestigious Oehms Classics label, and released a pair of albums devoted to Stravinsky and Glazunov in 2018.