Erykah Badu, Friday, March 16, at the Fillmore Auditorium, with Talib Kweli and Musiq Soul Child, arrived on the public stage in 1997, and since then her influence has been seen in established performers -- the solo Lauryn Hill frequently displays the lessons Badu taught her -- and worthy new artists such as Jill Scott, who even shares Badu's taste in head wraps. As a result, Badu (who doesn't need turbans as much as she once did, having recently shaved her head) is in danger of being overlooked or taken for granted: Witness the response to Mama's Gun, her new album, which remains mired in the middle of the sales charts and is receiving far less radio airplay than it deserves. That's a pity, because Badu is blooming creatively. Gun is a significant improvement over Baduism, her excellent debut disc, and must be counted as one of the finest albums from any genre to be released last year. Moreover, Badu remains a live performer of uncommon depth and range, capable of shifting from tender subtlety to funk toughness with apparent effortlessness, no matter the size of the venue. She's frequently imitated but never duplicated.