On a Higher Plane : A hotel bar is a lot like an international airport--but with better lighting and good martinis. And at the Four Seasons, a cool jazz singer.

What is it about hotel bars? Like an international airport, a good hotel bar can be anywhere in the world, and your fellow travelers are always as disparate and exotic as any odd colloquium waiting together to board a plane to Cairo, Paris, Auckland or Havana.

There is the barrel-chested, bald-headed lug in the wraparound sunglasses who looks as if his briefcase ought to be handcuffed to his wrist. Then there’s the leggy blond Breck Girl in the Betsey Johnson frock, drawing glances from a couple of nerdy guys in black tie, as well as a Mediterranean group who smokes Gitanos and talks about the restaurant business. Across the room, a couple of well-heeled 12-year-olds sip Virgin Marys and pretend not to know their parents at the next table.

But unlike international airports, hotel bars possess the significant virtue of offering good martinis and ambient lighting--the two things that perhaps ultimately compose the definition of cosmopolitan.

Like the Ritz in Paris or the Oriental in Bangkok, the Four Seasons is a quintessential phenomenon, the kind of place where you register under an alias as if you were a character in a Graham Greene novel. The ceilings are high, the plush carpet and comfortable sofas are done up in shades of decorous tan, the tables all have flowers, and there’s always a mirror somewhere that reflects you in a flattering light.

Also necessary to complete the scenario are a baby grand and a cool, sophisticated jazz singer. The Four Seasons’ Angela Carole Brown is just such a creature, with a rich voice that makes everything from Elton John to Edith Piaf sound just like Gershwin. Perched on a stool, she looks like an exotic falcon, with her head neatly framed in a cloche of black curls and the wide collar of her taffeta wrap dress nestled around her shoulders like wings. She exudes a kind of preternatural class that is uncommon in Los Angeles, where peacocks are more than rulers of the roost.

“She really belongs in New York, playing the Algonquin Room,” says Janine Coughlin, a former publishing exec who has moved to Los Angeles and was at the Four Seasons. “When I was starting out in publishing in New York, my boss used to go to the hotel bars, to the Algonquin, to the Carlyle to see Bobby Short. I would follow along, and it was impressive. It was something you had to do to be part of that world.”

Brown has been singing at the Four Seasons on Friday and Saturday nights for five years. Her musical background is eclectic.

“I made an album in 1989 in Japan. I did an off-Broadway play last year, a one-woman show called ‘The Purple Sleep Cafe.’ I do a lot of session work in the jazz vein. I am in the process of recording material for my own album. I have a studio in my home. I also sing with an all-female R&B; band. We play a lot of rock clubs around town. And I do jingles and ad voice-overs.”

She is quick to point out that just because the Four Seasons is a classy joint, it doesn’t mean one need be bullyragged by valets who are better dressed than you were at your own wedding.

“Sometimes friends will promise to come down and never do, and then I find out they’re intimidated by the fact that it’s a big hotel,” she says. “ ‘Oh, I have to get dressed up.’ But no, it’s really casual, warm and inviting. You don’t have to be in a tuxedo. I’ve been in other lounges in hotels and it’s very stark, and dark wood. There’s a really warm living-room vibe about this, which I really like.”

*

Where: The Four Seasons, 300 S. Doheny Drive, Los Angeles. (310) 273-2222.

When: Entertainment, 9 p.m.-1 a.m., Fridays and Sundays.

Cost: Martini, $8. Wine by the glass, $4.50-$15. Beer, $5. Bar menu, $8 and up.