Fiona Apple's singing voice sounds so cranky and weather-beaten, it's easy to forget that she's only 22. Easy, that is, until she chats up her audience between songs. 

Then she is the excitable, bare-armed baby sitter who became an instant pop phenom a mere three years ago. On her band's current tour, she said Wednesday at the Warfield, "all of us have agreed that, like, um, progressively the audiences have been getting, like, less loud and stuff.'' 

GENEROUS FANS

Her rambunctious San Francisco fans more than made up for it. They lavished the talented doe with gifts -- bouquets, framed art, a halter top that she changed into early in the set. 

"You're the most exciting crowd ever!'' she gushed near the end of the night, and she meant it. 

She means it all, which is why Apple is one of the more intriguing pop stars of recent years. So young, she already knows there's no time for indifference or false emotions. 

"I got my feet on the ground and I don't go to sleep to dream,'' she sang with unsmiling eyes on Wednesday. She is dead set on enjoying herself. 

She played every song from her superb second album, the one that bears the infamous 90-word title beginning "When the Pawn.'' Like a lot of her contemporaries, she followed conventional set-list wisdom (somewhere a consultant is making good money on these things), opening with the first two songs from the new album, then slipping her biggest hit, the tawdry-video song "Criminal,'' in the No. 3 slot. 

The outspoken Apple showed no sign of the tantrum that cut short a New York concert a few weeks ago. The only tantrums she threw Wednesday were with her gangly body, as she noodle-danced convulsively, like a woman trying to get out of a straitjacket.

In a sense, she is trapped: She's a melancholy baby in a time of vapid pleasantries, a word-drunk, wafer- thin blues mama trapped in the "Clueless'' generation. That such a powerful voice issues from such a slight body is a marvel of biology. When she played piano, she was barely there. When she flitted to center stage, her long, fine hair swayed like tinsel as she rocked with her microphone stand. 

Her band mates -- guitar, bass, drums, keyboard, vibes -- are all masters of dark L.A. pop, and they were done up in thrift-shop high- roller suits. Still, all eyes were fixed on the singer. 

PAST INFLUENCES 

After a quick, joyous opening set by the Los Angeles hip-hop group Jurassic 5, Apple took the stage to the sound of the Carpenters' "Superstar.'' The juxtaposition was about right: Apple plays piano-based torch pop with a rhythmic grounding (courtesy of drummer Matt Chamberlain) that could take place only in the hip-hop era. 

She also hints at much older styles -- saloon-style vamps, women's-lib-era Bacharach and country politan. "He said, 'It's all in your head,' and I said, 'So's everything,' '' she sang on the loping "Paper Bag.'' 

The singer worked herself into a frenzy on two of the new album's best songs, "A Mistake'' and "Fast as You Can,'' forcing her dry, husky voice up from her diaphragm. And then she was gone, barely 80 minutes after she had arrived. 

She skated back out for a brief encore, during which she belted Cole Porter's "Just One of Those Things'' to the accompaniment of a scratchy old recording. The band tore through a funky wah-wah version of Bill Withers' "Kissing My Love'' (kissing being one of Apple's biggest themes), and they were gone again. 

She has a confidence that mocks her 22 years. "Remember that depth is the greatest of heights,'' she writes somewhere in that crazy album title. The surprising depth of her music suggests that Apple could be around a long, long time. 

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