Jazz is a genre of music that originated in African-American communities during the late 19th and early 20th century. Jazz emerged in many parts of the United States of independent popular musical styles; linked by the common bonds of European American and African-American musical parentage with a performance orientation. Jazz spans a range of music from ragtime to the present day—a period of over 100 years—and has proved to be very difficult to define. Jazz makes heavy use of improvisation, polyrhythms, syncopation, and the swung note, as well as aspects of European harmony, American popular music, the brass band tradition, and African musical elements such as blue notes and ragtime. A musical group that plays jazz is called a jazz band.