"The change of pace in the jazz world accelerated during the middle decades of the twentieth century , almost as if music were a kind of science that could only justify itself by relentlessly superseding old paradigms and establishing new ones. The mandate of the day was to overcome obstacles, burst through the barriers, rewrite the laws of jazz, or even throw the whole rule book out the window. By the late 1950s, the final barriers in jazz were the music's continued allegiance to metrical rhythms, phrasing within the constraints of the chord, and maintenance of a tonal center. But within a few short years, these last precepts were challenged and rejected. In a very real sense, anything now seemed possible within the jazz idiom, the music's scope limited only by the imagination and bravado of its most visionary performers. This avant-garde movement, dubbed "free" jazz, asserted its proud independence from all traditions that had that had previously imparted structure to the music and ensured its commercial viability. For its most fervent advocates, the music was not just another style but the inescapable destiny of the art form."