The history of popular music is a pendulum constantly swinging from authenticity to artifice and back. This dialectic shapes and is in turn shaped by youth culture; baby boomers mirrored the bouncy, smiley, clean-cut early Beatles’ rapid transformation into the psychedelic, spiritual, hairy late Beatles. A generation later, the hair metal and synthpop of the ’80s gave way to the grunge and gangsta rap of the ’90s.