"A few years ago, mash-ups - eye-opening musical juxtapositions created by D.J.'s blending pieces from different songs - were the latest underground sensation. Then, last fall, Jay-Z, and Linkin Park released a collaborative album, "Collision Course," and the mash-up went mainstream. Now a new festival, AmsterJam, is coming to Randalls Island on Aug. 20 to celebrate the form with a roster of incongruous big-ticket pairings. Snoop Dogg will rap with the Red Hot Chili Peppers, the band 311 will play with the rapper Fat Joe, and the band Garbage will perform with Mos Def; a pairing of "two major Latin artists" is also promised. The curator of the event is Bootsy Collins, the legendary funk bassist who is something of a stylistic mash-up himself. Tickets go on sale Friday through Ticketmaster."