aksak, an important pattern in the rhythmic structure of folk and vernacular traditional music of the Middle East, particularly Turkey, Iran, and Afghanistan, and of the Balkans. It is characterized by combinations of unequal beats, such as 2 + 3 and their extensions, particularly 2 + 2 + 2 + 3. Called Bulgarian rhythm (e.g., by the Hungarian composer and ethnomusicologist Béla Bartók), the concept also includes divisions of the eight-beat structure common in Western music into unequal subdivisions, such as 2 + 3 + 3. As non-Western music, as well as eastern European folk music, began to exert influence in the West, aksak rhythms found their way into the works of a number of 20th-century composers of Western art music, Bartók and Igor Stravinsky foremost among them.