Bob's adds Cajun to its diverse mix

According to some official statistic, this city is 25 percent black. At dinner in most restaurants that number seems impossibly high. Black and white diners just aren't eating at the same establishments. On a Friday or Saturday night, the packed houses and endless waits at Teatro, Mistral, or any place in the North or South End don't include many exasperated black faces. For years, a lot of them have been enduring long waits for a table at Bob the Chef's, Darryl Settles's soul food joint, which has just undergone a name change and a menu expansion. Now it's called Bob's Southern Bistro and serves a variety of Cajun dishes.

Eating at Bob's is like eating in another city. There are black people and white people, Spanish and Portuguese speakers, some Asians, a few Arabs, and folks who look like they could be from everywhere. Sometimes they're all at the same table. The place is small. It's often cramped and always filled with a soothing mix of races who've come for chicken and waffles, mustard-fried catfish, and, now, shrimp etouffe. There's also jazz. It's often played by energetic interracial and international trios and quartets. If you've shown up for a quiet, romantic evening, even the gentlest band seems loud. But no one shows up at Bob's to whisper sweet nothings. You go as culinary foreplay to whatever you might be up to afterward.

Some couples can't wait. There must be something in the Creole jambalaya, a pleasing concoction of chicken, sausage, shrimp, and steamed mussels that has a polite kick. The menu warns that spices used are not for the timid, but those feeling bold should insist on ''extra spicy" anyway -- just in case the cooks are feeling timid themselves. The fried chicken is reliably crispy and the Belgian waffle that accompanies it is fluffy. The liver and onions come well cooked and thinly sliced. They're best eaten with collard greens, which have a lovely smoky flavor.

Bob's is so busy it might be understaffed. But where would more waiters stand? In any case, an entrée might take longer to appear than growling stomachs prefer, but the servers aren't off somewhere on their cellphones. Parties can balloon to 20 people, and the crew works hard to stay attentive.

This includes arriving with a cake and belting out birthday wishes. At Chili's or the Cheesecake Factory, and even at some upscale places, the wait staff has been known to warble out a respectable, perfunctory ''Happy Birthday to You" to a shocked and embarrassed diner. Not so at Bob's. When the staff sings ''Happy Birthday," they use the elated Stevie Wonder version, which Wonder wrote for Martin Luther King Day. And the birthday girl doesn't cover her mouth in surprise. She gets up and sings along with the rest of the table -- and part of the restaurant. Suddenly, everybody feels like Martin Luther King Jr.

If you're used to this sort of dining, your response to such mixed company could be: ''Big deal." If you're not, the sight could turn you anthropological. And if you're used to eating this way but rarely experience it, this loud, crowded place, with good music and evocative soul food should feel like home.

Bob's Southern Bistro, 604 Columbus Ave., 617-536-6204, www.bobssouthernbistro.com. Entrees: $5.95-$15.95.