Folk Music: In popular usage, this term refers to music of oral traditions, often in relatively simple style, primarily of rural provenance, normally lacking an identifiable composer and performed by non-professionals, used and understood by broad segments of a population and especially by the lower socioeconomic classes, characteristic of a nation, society, or ethnic group, and claimed by one of these as its own. Since this is a romanticized picture that has often been imbued with political significance, the term "folk music" is avoided by specialists in ethnomusicology,the study of musical cultures.
Traditional Music: A term used by ethnomusicologists in preference to "folk music," this refers to types of music that are handed down within a particular culture, by a variety of means that may include oral transmission, written notation, study with professional teachers, or improvisation within culturally-defined parameters. Traditional music may have a place in society that makes it more like the Western conception of "classical" music than like "folk" music, but it does tend to be associated with rural societies or conservative areas of society.
Popular music: Music accessible to a wide audience, distributed through the mass media as a commercial product. It tends to be associated with urban rather than rural cultures, and is performed by professional musicians.
Jazz: An eclectic, expanding collection of 20th-century styles of American origin, owing much to both black and white American musical cultures. It is more dependent on group improvisation and spontaneity than classical music, which is fixed in a written score. Instrumental ensembles tend to emphasize winds more than strings, and many pieces take the form of a series of variations a chord progression derived from a popular song.
Spiritual: A religious song used in English-speaking "free churches," especially in the United States, close to the style of popular music in the eighteenth and early nineteenth centuries. Related types were cultivated by both whites and blacks throughout the 19th century and into the 20th.
Gospel Music: The successor to spirituals, consisting of religious songs close to the style of late-nineteenth-century popular music. As with the spiritual, there are both white and black varieties.
Rhythmic Polyphony: The simultaneous use of two or more contrasting rhythms. It is a common element in African and African-American music.
Call and Response: Alternation between two performers or groups of performers, especially between a solo singer and a group of singers. Black American work songs and gospel music make use of this device, which may have derived from "free church" preaching style. American popular music adapts it, for example, in interplay between a blues or rock singer and a guitar, two sections of a jazz ensemble, and a soul singer and audience.
Improvisation: The spontaneous creation of music in the course of extempore performance. There is, however, always a model or framework that determines the scope within which a musician may create. In the case of jazz, the model may be a series of harmonies that determine pitches to be selected for a melody; or a melody that is subjected to variation; or a set of motives from which selection is made.