Anita Baker, a storm center of hyperactivity, darts around the Philadelphia Academy of Music trailing a mike cord. Stylish but childlike in a yellow sweatshirt and white slacks, the 5', 90-lb. powerhouse ducks into a dark corner, sings a lush, jazzy phrase, then dances back to center stage to deliver her instructions to the technicians. "There's distortion on top of me," she says. "I want to use this hall."

The sound check, already in its second hour, may well run longer than tonight's performance—one of 77 on Baker's current sold-out tour. "I ain't leaving until everything is done, yes, Lord," says Baker, 28, the uplifting echo of a Baptist revival tempering the intensity of her perfectionism. The crew is frayed but tolerant. "I'm a bit ragged," says the sound man, "but she's so exceptional, I don't mind. It's that voice."

That voice. Technically a contralto, Anita Baker's voice is in fact a natural wonder. Deep and richly textured, it can plunge to sultry depths and leap octaves in a single bound. She has a successful album, Rapture, on the charts, but what's far more impressive—and far less quantifiable—is the word-of-mouth about her talent. People talk about Anita Baker. Her New York solo debut this spring sold out despite little advance publicity. Stevie Wonder calls her a "wonderful, wonderful talent" who reminds him of "what Sarah Vaughan sounded like when she was younger." Patti LaBelle calls her "one of a kind. People probably thought she was some kind of cookie, but she's the whole cake." After her performance at New York's JVC jazz festival, the New York Times dubbed her "one of the decade's two or three most promising pop soul singers."

Four years ago Baker was only the most promising receptionist at a law firm in Detroit, her hometown. An inner-city kid steeped in gospel singing, she had already made one five-year stab at a musical career and come up empty. "I was a Chaka Khan clone," she says of her most successful stint, nearly three years fronting a "drop-kick-you-in-the-chest" funk band called Chapter 8. "We would do four sets a night," she recalls. "We'd sweat buckets and go do more." But when the band released an LP that evaporated, says Baker, "I put away my double-knit hip-huggers and halter slingshot costumes and thought that was it." She says that the choice wasn't as traumatic as it sounds because she was raised, primarily by her aunt, to be pragmatic. "I gave singing a 100 percent shot, but it was like 'Plan A didn't work, so try plan B. Get a job, sister.' " Her voice helped her land the receptionist job, and everything seemed settled. "My aunt could tell her friends that I was a professional. I was making five figures a year; $10,000 was a lot to me."

There she might have stayed had not Otis Smith, an independent producer who had heard her work with Chapter 8, called to suggest that she record a solo LP. "At first I said, 'Nah,' " she remembers. "Hey, I had Blue Cross and Blue Shield and a paid vacation, but he dangled bait at me." When Smith offered to match her receptionist's salary and pay her living expenses if she would move to L.A. and record, Baker bit. Although their partnership proved a fiasco for her—the pair wound up in prolonged litigation—she was able to record a solo album, Songstress, that advertised her talent to the industry.

Now signed with Elektra Records, Baker served as Rapture's executive producer, which enabled her to select songs that reflected the styles of her favorite singers: Vaughan, Nancy Wilson and the low-moaning Mahalia Jackson, whom Baker calls "the only woman I heard when I was young who didn't make me feel like a misfit."

She has a "very, very serious" relationship with a Washington, D.C.-based businessman she met in a shoe store two years ago. ("His name is Walter, and he's in marketing at IBM, but I want to keep it a secret.") Like everything else, their get-togethers, for now, are scheduled around her hectic travel and performance routine. Her one complaint, she says, is that for the last nine months she hasn't had a chance to "go home and feel what has happened, to soak it in. I got my first gold album with Rapture, and they brought it to me and I held it in my arms for five minutes. Then I had to go to L.A. Then my song Sweet Love was on Moonlighting, and I wasn't able to watch it: I was working. And I was on the Today show, but I couldn't see it because I had to travel. I miss everything."

And what does she miss most? "If I could be doing anything," says Baker, "I'd be laying on the floor in my birthday suit eating junk food and watching something dumb on TV." Sometimes even a crackerjack performer needs a break.