Cause of death: polycythemia
Béla Viktor János Bartók (; Hungarian: [ˈbeːlɒ ˈbɒrtoːk]; 25 March 1881 – 26 September 1945) was a Hungarian composer, pianist and ethnomusicologist. He is considered one of the most important composers of the 20th century; he and Franz Liszt are regarded as Hungary's greatest composers. Through his collection and analytical study of folk music, he was one of the founders of comparative musicology, which later became known as ethnomusicology.
Source : Wikipedia
