"This album contains no instruments other than the human voice." So read the liner notes to "Good News," the Persuasions' tenth album in a glorious 20-year career; it's also one of the best efforts ever by this a capella rhythm & blues quartet.

The sound has a crisp clarity that helps the listener follow each voice as it leaps and dives to find its position in the group's surprisingly full sound. At the same time, though, there's a welcome looseness. Instead of carefully arranging each four-voice chord, there's room for the singers to improvise and embellish, lending the songs the spontaneous sense of discovery that real street-corner singing offers.

Rather than the classic doo-wop usually associated with a capella, this session emphasizes the soul music that followed doo- wop. Lead singer Jerry Lawson chooses from two of his favorites as he sings four Sam Cooke songs and two David Ruffin songs. He strips down the Motown sound to bare basics on a dramatic version of Ruffin's "I Lost Everything." Lawson may not have Cooke's voice, but his joyful shouts, growls and whoops give the songs an irresistible momentum. ON RECORD, ON STAGE THE ALBUM THE PERSUASIONS -- Good News (Rounder 3053). THE SHOW THE PERSUASIONS, with Phoebe Snow at the Wax Museum on Thursday at 9.