What is Bela Bartok best known for?

Béla Viktor János Bartók (pronounced /ˈbɑrtɒk/ (Wells 1990), Hungarian pronunciation: [ˈbeːlɒ ˈbɒrtoːk]) (March 25, 1881 - September 26, 1945) was a Hungarian composer and pianist. He is considered to be one of the greatest composers of the 20th century and is regarded, along with Liszt, as his country's greatest composer (Gillies 2001). Through his collection and analytical study of Folk Music, he was one of the founders of ethnomusicology