The Beach Boys emerged in the 1960s already sounding nostalgic for a simpler time that had just begun receding into the past. By the time they became a touchstone for indie rock decades later, that nostalgia had folded over and began to function on multiple levels. Something similar is at work when, say, Lupe Fiasco uses a sax sample from 1971 to remind hip hop fans of a 1992 song, Pete Rock & CL Smooth's "They Reminisce Over You (T.R.O.Y.)," a song which itself contained a personal tale of nostalgia for a fallen friend. Hip hop always builds on memories of the past, but few have been so openly nostalgic for the good old days as a new generation of artists like Joey Bada$$ are, often for an era of the '90s that they barely remember themselves.