Before hip-hop’s gestation in the boroughs of New York, The Last Poets fused bongo beats and spoken word, building fervor for people whose voices were/are muzzled in popular culture. After releasing their first album in 1970, the poets garnered “griot” status, and began collaborating with the Black Panthers. Their dithyrambic verses prefigured the gritty, firebrand raps of KRS-One and Public Enemy. Laced with such classics as “Gashman,” “When the Revolution Comes,” and “This is Madness,” new two-CD box set will appeal to armchair poetry buffs and rabble-rousers alike.