From my History of the Rock & Roll Era class comes this brief glimpse into the art of the mash-up . While some form of embryonic mash-up existed since the early days of recorded music -- either as tape-driven sound collages or musique concrète -- the advent of sampling in hip-hop opened up the creative floodgates, as the end of the 20th Century offered three landmark recordings that significantly advanced the art form as sampling moved from analog to digital. First came the landmark "Pump Up The Volume" by M|A|R|R|S (a U.K. #1 single from 1987): Following the single release of "Pump Up The Volume" -- as well as the sample-heavy album work of hip-hop producers Prince Paul (De La Soul) and The Bomb Squad (Public Enemy) -- Endtroducing... (1996) by DJ Shadow and Since I Left You (2000) by The Avalanches were LP's built entirely from samples, often taking years to produce. Here's "Frontier Psychiatrist" by The Avalanches, which takes the sa