The lighter, softer second voice on Abbey Lincoln's 1998 album Wholly Earth (Verve) belongs to Chicago vocalist Maggie Brown--but only Lincoln's thick, smeary timbre could make Brown sound light or soft. At last year's Chicago Jazz Festival she parlayed a ten-minute set into a restrained but powerful tribute to gospel pioneer Thomas A. Dorsey (whose 1999 centennial was mostly overshadowed by Duke Ellington's), punching a hole in the expectations of those who knew her only as a fledgling pop singer. And her other gig at that festival--an afternoon show on the new children's stage that traced the African diaspora in kid-friendly musical terms--made clear that she's inherited the formidable storytelling skills of her father, legendary jazz singer Oscar Brown Jr. In retrospect, I suppose Brown's strong narrative sense and predilection for gospel were both lurking beneath the pop veneer of her self-released 1995 disc, From My Window, but now she gives each of those elements the attention it deserves, and to exhilarating effect. She brings confident intonation and polished expressivity to everything she sings; whether she's purring or roaring, her transparent voice has just enough honey, a deep-soul sweetness instead of a sugary surface. Brown has promised to explore some of the middle ground between gospel and jazz at this performance, accompanied by a quartet. She's one of six acts slated for the Jazz Institute of Chicago's 21st annual Jazz Fair, which runs all evening on Thursday the 27th and also includes jazz films, a panel discussion, and a merchants' midway. Related events continue through the 30th; see the jazz listings in this section or www.jazzinstituteofchicago.org for details. Thursday, January 27, 6:30 PM, Randolph Cafe, Chicago Cultural Center, 78 E. Washington; 312-427-1676. Brown also gives a free in-store performance Saturday at 2 at Borders Books & Music, 830 N. Michigan; 312-573-0564.