BOB MARLEY: ''Chant Down Babylon'' (Tuff Gong/Island). The basic idea has an undeniable tinge of morbidity, but this assortment of posthumous duets between the Abraham of reggae music and some of his spiritual (and actual) progeny frequently triumphs. Unlike similar studio excavations of Frank Sinatra, this one turns its trickery into hip-hop, a music grounded in historical revision. The talent is top-notch on both sides of the mortal divide. Stephen Marley, who led the project, chose songs that would feel fresh to old Marley fans and revelatory to new ones. His remixes honor hip-hop's link to dub rhythms. And his crew, including Lauryn Hill, Busta Rhymes, Erykah Badu, Krayzie Bone and Guru, exercise their wits to go beyond idol worship, making these urgent, timeless songs speak anew. ANN POWERS