Erykah Badu with Nikka Costa

When Erykah Badu delivered her debut album, Baduizm, in 1997, she stood out like a refreshingly sore thumb from the pack of R&B vocalists trying to win imaginary It's Showtime at the Apollo contests. It's hard to remember now, but just four years ago R&B seemed less about good songwriting and more about how many notes could be stretched into a word at the end of a phrase.Then Badu came along, with her thin, reedy but evocative voice, and changed everything. She brought phrasing derived as much from jazz as from soul, with a little bit of pop thrown in. She wrote songs that rode blistering grooves without abandoning melody, and she wrote melodies that refused to succumb to clichés. She took inspiration from hip-hop, with its scattershot internal rhymes and its breathless personal revelations. Beyond this artistic achievement, Badu became a big star, selling records by the millions and sending legions of A&R reps to the trenches to find people like her. In Badu's wake, we have India.Arie, Lauryn Hill, Jill Scott, Alicia Keys, Blu Cantrell, Sunshine Anderson and many other female vocalists doing their own thing: making music as sexy and physical as R&B has ever been while retaining an individual personality. Badu's second studio album, Mama's Gun, came out last year and proved a worthy follow-up. She recruited ?uestlove from the Roots to play drums on most tracks and hired Roy Hargrove, Roy Ayers and Betty Wright to drop in on some. The result is even funkier than her previous work, and her voice sounds more relaxed and comfortable.

Opening for Badu on this tour is Nikka Costa, whose recent album Everybody's Got Their Something is making a splash with a heavier rock-to-R&B ratio, similar to some of Lenny Kravitz's work. People have been talking about her appearance on the last episode of Chris Rock's TV series for months; she could push Badu to work a lot harder.