In the 20s, jazz meant one very specific thing; in the 50s it meant another very specific thing. By the end of the century, jazz had mutated so many times, it was less a genre than a signifier of loose good vibes. These songs circle jazz like electrons around a nucleus. Archie Shepp played jazz with a funk wallop; David Sanborn was a major player of the unfairly maligned smooth jazz. Steely Dan spent meticulous studio sessions building an unstudied jazz atmosphere, while The Roots brought the spontaneity and nuance of jazz instrumentation to hip-hop.