The NYT takes notice of mash-up ("versus") remixes, like the Public Enemy vs. Dexy's Midnight Runners mix that gets me up out of my seat every time.
Making new songs out of existing works, of course, is nothing new. There are precedents in everything from 20th century classical to cartoon music, and it is the cornerstone of hip-hop, be it early pioneers like Grandmaster Flash or later innovators like Dr. Dre. In the 80's and 90's, avant-garde sound artists like Plunderphonic, Negativland and the Tape-Beatles (as well as the pop pranksters the KLF) challenged copyright law with collages made of everything from found sounds to top 40 hits. But many musical observers trace the official beginnings of the British bootleg scene to the Evolution Control Committee, which in 1993 mixed a Public Enemy a cappella with music by Herb Alpert.