Jazz is a kind of music characterized by blue notes, syncopation, swing, call and response, polyrhythms, and improvisation. Though originally a kind of dance music, jazz has now been "long considered a kind of popular or vernacular music (and has also) become a sophisticated art form that has interacted in significant ways with the music of the concert hall". Jazz's development occurred at around the same time as modern ragtime, blues, gospel and country music, all of which can be seen as part of a continuum with no clear demarcation between them; jazz specifically was most closely related to ragtime, with which it could be distinguished by the use of more intricate rhythmic improvisation, often placing notes far from the implied beat. The earliest jazz bands adopted much of the vocabulary of the blues, including bent and blue notes and instrumental "growls" and smears.