If there ever was a clear border between hip-hop and activist poetry, Saul Williams crashes through it on his album “The Inevitable Rise and Liberation of Niggy Tardust” ( niggytardust.com ). He declaims, chants, narrates and sings his visionary takes on the African-American condition and his own sense of purpose. Instead of slogans or polemics Mr.

Williams slings hallucinatory images — “A rabid dog in heat on a dead end street” — while his producer, Trent Reznor of Nine Inch Nails, turns each track into a projectile. Thudding old-school drumbeats, looming synthesizers and sudden empty spaces give the songs clout, with verbal and nonverbal hooks. Their sense of impending mayhem harks back to Public Enemy at its peak. Like Public Enemy, Mr. Williams wants his album heard, not just sold.

It’s available on his Web site, for a $5 donation or free. TUNNG Folkies with a laptop and mortality on their minds, the English group Tunng explores the aesthetics of interruption on its third album, “Good Arrows” (Thrill Jockey).

Pretty webs of acoustic picking are blotched with static and ratchety clatter or punctuated with arbitrary spoken-word samples, while placid, smoky voices offer thoughts like “We sing as the sky collapses.” The disruptions ensure that the songs don’t ease by unnoticed; every buzz and ping reinforces the disquiet. ‘THE ROOTS OF CHICHA’ The steady clip-clop of cumbia runs through Andean music old and new, and Peruvian rockers embraced it during their hippie era.