African Rhythm

Jazz is a rich mixture of many types of musical influences. However, it's black roots can be traced back to Africa where music tended to be based on simple melodies and complex cross-rhythms, in contrast to European music which tended to use complex harmonies and simpler rhythms. 
The slaves from Africa brought their music with them. But polyrhythmic drumming, ring shouts and strange songs created fear in the white population, fear of rebellious communication and insidious Voo Doo ritual. African influences were frequently outlawed and instead slaves were encouraged to convert to the regular church music. A blind eye was turned to the work songs for obvious reasons.
Influences from Africa started in New Orleans around 1820 in Congo Square but the big influx of free blacks from the rural South and the West Indies was unleashed at the end of the Civil War in 1865.

The main 'black threads' were -

* music which was mostly sung and developed from the distinctive sounds from the work songs on the plantations, the 'field hollers' which were transplanted into the characteristic songs of the churches, Baptist hymns and the Spirituals

* 'vocalisation' which was initially led by drum music (talking drums) with cross rhythms and syncopations 

* 'part' music, with simultaneous horizontal rhythmic lines

* flexible expressions and 'dirty' timbre - growls, slurs, vibrato, glissandi, bends, scoops - and general irreverence, adding interest from the unexpected   

* ‘new’ pentatonic and 'blues' scales, the 'folk music' scales which replaced the 'difficult' fourth and seventh half tone steps with unfathomable blue notes, somewhere in between the half steps, neither B nor B flat 

* functional music, which was a vital part of everyday social routine, participation, particularly four square rhythms for dancing and 'call and response' involvement

* the repetitive hypnotic hysteria of 'Voodoo' and ring shouts, repetitive 'choruses' building momentum to the 'ride out

* and banjos!

Jazz emerged from an ongoing fusion of African rhythmic and European harmonic influences.