A musical art form that originated in New Orleans around the start of the 20th century. Jazz uses improvisation, blue notes, swing, call and response, polyrhythms and syncopation, and blends African American musical styles with Western music technique and theory. Jazz has roots in the combination of West African and Western music traditions, including spirituals, blues and ragtime stemming from West Africa, New England's religious hymns, hillbilly music and European military band music.

After originating in African American communities near the beginning of the 20th century, jazz styles spread in the 1920s, influencing other musical styles. The instruments used in marching bands and dance band music at the turn of century became the basic instruments of jazz: brass, reeds and drums, using the Western 12-tone scale. Small bands of black musicians, mostly self taught, who led funeral processions in New Orleans played a seminal role in the articulation and dissemination of early jazz, travelling throughout black communities in the Deep South and to northern cities.

As racial equality of opportunity improved in the US, many African-American musicians developed more formal music skills which helped to preserve and disseminate the essentially improvisational musical styles of jazz. Rhythms brought from a musical heritage in Africa were incorporated into cakewalks, coon songs and the music of 'jig bands', which eventually evolved into ragtime around 1895. The music, vitalised by the opposing rhythms common to African dance, was vibrant, enthusiastic and often extemporaneous. Early ragtime music was in the format of marches, waltzes and other traditional song forms but the consistent characteristic was syncopation. Scott Joplin published the first of many ragtime compositions.

An early style of jazz called Dixieland developed in the New Orleans area, which had long been a regional music centre with a large African-American population. The New Orleans style used more intricate rhythmic improvisation than ragtime and incorporated blues elements, including bent and blue notes, and used the European instruments in novel ways. Key figures in the development of the new style were trumpeter Buddy Bolden and his band and Kid Ory, a trombonist who refined the style.

In the northeastern United States, a 'hot' style of playing ragtime developed, characterised by rollicking rhythms, without the bluesy influence of the southern styles. The music had collective improvised solos around a melodic structure, that ideally built to a climax, supported by a rhythm section of drums, bass, banjo or guitar. The solo piano version of the northeast style was typified by Eubie Blake. 'Stride' piano playing, in which the right hand plays the melody while the left hand provides the rhythm and bassline, was developed by James P. Johnson who influenced later pianists like Fats Waller.

In Chicago in the early 1910s, saxophones vigorously 'ragged' a melody over a dance band rhythm section, blending New Orleans styles and creating a new Chicago jazz sound. Characterised by harmonic, inovative arrangements and a high technical ability of the players, artists such as Benny Goodman and Gene Krupa helped to pioneer this style.

Along the Mississippi from Memphis to St. Louis, the 'Father of the Blues' W.C. Handy popularised a more accessible approach in which improvisation was limited to short fills between phrases.

With Prohibition in the 1920s, speakeasies emerged as nightlife settings and many early jazz artists played in them. In parallel, the development of recordings and radio helped popularise jazz music. The banjo was the standard stringed, chord-playing rhythm instrument in jazz ensembles of the 1920s. Even as late as the early 1930s, sophisticated jazz orchestras such as Duke Ellington's still used a banjo.

In the late 1930s, however, several guitarists helped to pave the way for the introduction of guitar into jazz ensembles. Lonnie Johnson, a New Orleans-born guitarist, was one of the early guitarists to perform single-string (as opposed to chord-based) guitar solos. Lonnie performed with and influenced guitarist Eddie Lang, who also performed with jazz violinist Joe Venuti and many of the white jazz bands from the 1920s.

The 1930s was the era of swing. While the solo became more important in jazz, most of the jazz groups were big bands, such as Benny Goodman's Orchestra, Duke Ellington and Louis Armstrong. Swing was also dance music, which served as its immediate connection to the people. Although it was a collective sound, swing also offered individual musicians a chance to improvise melodic, thematic solos which could at times be very complex.

As racial segregation began to relax, white bandleaders began to recruit black musicians such as vibraphonist Lionel Hampton, guitarist Charlie Christian (who developed an influential style of 'single string' electric guitar soloing)and trumpeter Dizzy Gillespie. Vocalists such as Bing Crosby, Ella Fitzgerald and Billie Holiday were also influenced by Armstrong's style of improvising and the scat style later spread to other vocalists such as Frank Sinatra and Sarah Vaughan.

Kansas City jazz in the 1930s marked the transition from big bands to the bebop influence of the 1940s. Characterised by soulful and bluesy stylings of big band and small ensemble swing, arrangements often showcased highly energetic solos from artists such as alto sax pioneer Charlie Parker.

Outside the USA, the beginnings of a distinctly European jazz started emerging. At first this came mostly in France with the Quintette du Hot Club de France being among the first non-US bands of significance to jazz history. In particular, the playing of Belgian guitarist Django Reinhardt who recorded with the Quintette du Hot Club de France with violinist Stéphane Grappelli would be important to the rise of gypsy jazz, which is one of the earliest genres to start outside the US and is an unlikely mix of 1930s American swing, French dance hall 'musette' and the folk strains of Eastern Europe.

In the mid-1940s, bebop performers such as saxophonist Charlie Parker, pianist Bud Powell and trumpeter Dizzy Gillespie helped to shift jazz from danceable pop music to a more challenging form. Differing greatly from swing, bebop divorced itself early on from dance music, establishing itself as art form but severing its potential commercial value. Other bop musicians included pianist Thelonious Monk, trumpeter Fats Navarro, saxophonist Sonny Stitt and drummer Max Roach. The beboppers borrowed from the innovations of key earlier musicians - in particular, Coleman Hawkins, Lester Young and Art Tatum - and carried their ideas several steps further, introducing new forms of chromaticism and dissonance into jazz. Where many earlier styles of jazz improvisation kept close to the basic key and melodic line of the piece, bebop soloists engaged in a more abstracted form of chord-based improvisation. The style of drumming also shifted, from the earlier 4-to-the-bar bass drum pulse to a more elusive and explosive style where the ride cymbal was used to keep time while the snares and bass drum were used for unpredictable accents.

These divergences from the jazz mainstream of the time initially met with a hostile response among fans and fellow musicians, but it was not long before bebop's influence was felt throughout jazz. By the 1950s, bebop had become an accepted part of the jazz vocabulary, and it has gradually over the years come to form the bedrock of modern jazz practice.

Free jazz and avant-garde jazz are partially overlapping subgenres that, while rooted in bebop, typically use less compositional material and allow performers more latitude. Free jazz uses implied or loose harmony and tempo, which was deemed controversial when this approach was first developed. Early performances of these styles go back as early as the late 1940s and early 1950s. The bassist Charles Mingus is frequently associated with avant-garde jazz, although his compositions cover a myriad of styles and genres. The first major stirrings of what became free jazz were in the 1950s, with the early work of Ornette Coleman and Cecil Taylor. In the 1960s, performers included John Coltrane, Archie Shepp, Sun Ra, Pharoah Sanders and Dewey Redman. Coleman, Taylor and Sanders continue to play in this style and other more recent exponents include Keith Jarrett.

Mainstream jazz emerged as a loose jazz style in the late 1970s and 1980s and featured more harmonic tones and softer dynamics.

Latin jazz emerged as a major subgenre in the 1950s and 1960s in 2 main varieties: Afro-Cuban and Brazilian. Afro-Cuban jazz bands were started by notable bebop musicians such as Dizzy Gillespie. Brazilian jazz is synonymous with bossa nova, a Brazilian popular style which is derived from samba with influences from jazz as well as other 20th-century classical and popular music. This alternative to the 1960s hard bop and free jazz styles gained popular exposure by West Coast artists such as guitarist Charlie Byrd and saxophonist Stan Getz.

In the 1970s, with such artists as Keith Jarrett, Paul Bley, Pat Metheny, Jan Garbarek, Ralph Towner and Eberhard Weber, the ECM record label established a new jazz style, featuring mainly acoustic instruments and incorporating elements of world music and folk music. This is sometimes referred to as European or Nordic jazz, despite some of the leading players being American.

In the late 1960s and early 1970s, the hybrid form of jazz-rock fusion was developed, typically including a number of electric instruments (electric guitar, electric bass, electric piano, synthesizer keyboards) and often using mixed metres, odd time signatures, syncopation and complex chords and harmonies. Although jazz purists protested the blend of jazz and rock, some of the leading jazz innovators crossed over from the contemporary hardbop scene into fusion, including Miles Davis, keyboardists Chick Corea and Herbie Hancock, drummer Tony Williams, guitarists Larry Coryell and John McLaughlin, Frank Zappa, Al Di Meola, jazz violinist Jean-Luc Ponty, Sun Ra, Narada Michael Walden, Wayne Shorter and bassist-composer Jaco Pastorius. Perhaps the most successful were McLaughlin's Mahavishnu Orchestra and Weather Report, which brought together Josef Zawinul and Shorter who were joined by a large and changing number of world musicians including Pastorius, Miroslav Vitous and Airto Moreira.

In the 1980s, the jazz community shrunk dramatically and split. A mainly older audience retained an interest in traditional jazz styles as played by Wynton Marsalis. A lighter form of fusion, often called smooth jazz or jazz-pop, was performed by artists such as saxophonists Kenny G and Grover Washington.

Most recently, jazz elements have become blended with modern urban music styles through the work of Norah Jones and Amy Winehouse, although these do not really qualify as jazz.

Jazz as a genre is often difficult to define, but improvisation is a key element of the form. Improvisation has been an essential element in African and African-American music since early forms of the music developed and is closely related to the use of call and response in West African and African-American cultural expression. The form of improvisation has changed over time. Early folk blues music was often based around a call and response pattern and improvisation would factor in the lyrics, the melody or both. In Dixieland jazz, musicians take turns playing the melody while the others improvise countermelodies. In contrast to the classical form, where performers try to play the piece exactly as the author envisaged it, the goal in jazz is often to create a new interpretation, changing the melody, harmonies, even the time signature.

By the swing era, big bands played using arranged sheet music, but individual soloists would perform improvised solos within these compositions. In bebop, however, the focus shifted from arranging to improvisation over the form: musicians paid less attention to the composed melody, which was played at the beginning and the end of the tune's performance with improvised sections in between. Later styles of jazz abandoned the strict notion of a chord progression, allowing the individual musicians to improvise more freely within the context of a given scale or mode. The avant-garde and free jazz idioms go even further in abandoning chords, scales and rhythmic metres.