The Genius of Jazz.
Jazz musicians of the 1940s and 1950s incorporated improvisation into the music - playing with unique phrasing during solos. As America's new art form grew in popularity, musicians like Charlie Parker, Dizzy Gillespie, Thelonious Monk, and Miles Davis evolved jazz into an intellectual, creative, and innovative form of music. This new style of jazz was called Bebop.
In the 1940s, as jazz music became more sophisticated and intellectual, jazz musicians started to completely leave the written music and improvise. Improvisation was a key element of jazz. Musicians would have conversations on stage through their instruments. Music is its own language.
This type of jazz was mostly performed in New York City which boasted a plethora of jazz clubs at the time. One of the jazz clubs that cultivated this exciting new form of jazz was Birdland. This is when jazz music became less danceable like swing jazz - jazz music of this era was more cerebral or serious - interesting to sit and listen to, but not good for dancing.
Jazz groups were smaller - trios and quartets were popular. People call this the heyday of jazz because jazz was enjoying a peak in popularity with scores of innovations happening during this period. Jazz artists of this era would improvise with their singing or scat.
One important thing about improvisation is that it felt free. It represented freedom.
One of the reasons it was so important for musicians to have freedom of improvisation is because many of the jazz musicians were black and during the 1940s and 1950s in America, segregation was still in effect. People were growing weary of Jim Crow laws at this time and the beginnings of the Civil Rights Movement were brewing.
And - jazz was part of it.