<Tr> <Td_colspan="2"> <Ul> <Li> Contemporary folk music </Li> <Li> popular music </Li> <Li> roots revival </Li> <Li> vernacular music </Li> </Ul> </Td> </Tr> <Ul> <Li> Contemporary folk music </Li> <Li> popular music </Li> <Li> roots revival </Li> <Li> vernacular music </Li> </Ul> <Li> Contemporary folk music </Li> <P> Folk music includes both traditional music and the genre that evolved from it during the 20th century folk revival . The term originated in the 19th century, but is often applied to music older than that . Some types of folk music are also called world music . Traditional folk music has been defined in several ways: as music transmitted orally, music with unknown composers, or music performed by custom over a long period of time . It has been contrasted with commercial and classical styles . </P>

Who were the partners for the ethnomusical study of rural and folk music begun in the 1930s