When you walk into the Glass House, in the heart of New Orleans' toughest neighborhood, it's difficult at first to find the band. There's no stage, not even any stage lights, and the Dirty Dozen Brass Band's rumbling jazz seems to come at you from all four walls. The living room-size club is packed with bobbing, weaving heads and shoulders underneath a low ceiling of Christmas tinsel and Mardi Gras beads.

As you elbow through the crowd toward the far wall, you finally see that the last two rows of dancers are holding horns and drums. What sounded like a funky electric bass line turns out to be Kirk Joseph's tuba. What sounded like two full drum sets is no more than Jenelle Marshall's snare drum and Benny Jones' bass drum. What sounded like ambitious keyboard arrangements are a trombone, two trumpets and two saxophones. Playing without amplification, the eight musicians turn Thelonius Monk's "Blue Monk" into a slow grind dance number.

The Dirty Dozen Brass Band, which opens the Capital City Jazz Festival at the Washington Convention Center tonight, has been hailed for incorporating Duke Ellington, Charlie Parker and James Brown into the New Orleans parade band tradition. These accolades notwithstanding, every Monday night that they're home in New Orleans, they return to the Glass House, the battered ghetto club where they got their start. With a $1 cover, it's the best entertainment bargain in America.

"At a concert," says trumpeter/leader Gregory Davis, "people are 20 to 30 feet away. You can't touch them. At the Glass House, though, people are dancing just two feet away, and it makes you want to work harder. I mean, I'm going to look at you funny if I'm up there working my butt off and you just sit there watching me. I want you to get up and get sweaty and funky too. At the Glass House, everybody gets into it. It's the best gig I've ever played."

Davis leads the band in the title song from their first album, last year's "My Feet Can't Fail Me Now" (Concord). As he chants the refrain, he marches in place at the back of the bar, swiveling on one foot and then the other. The next morning Davis, 28 and sporting a neat green polo shirt, talks about the band's origins.

"This is a great city for parades!" he exclaims. "In New York or Washington, people will stand on the sidelines at a parade and wave. You could start a parade right here in this corner right now and go 25 miles around the city and 10,000 people would join in. The people make the parade -- they're not content to just watch it go by. They sing and dance and beat on anything they can find."

"And at the end of 25 miles," chimes in snare drummer Jenelle (Chi-Lite) Marshall, "they'll complain if you want to stop. They take care of you, though. They'll hand you crawfish and cups of beer as long as you keep playing. They'll even wipe your face. It makes the musicians work harder."

As loose as New Orleans parades are, the established brass bands had a set way of doing things with a set repertoire. This is what got the Dirty Dozen into trouble -- they wanted to play the Charlie (Bird) Parker and Miles Davis tunes they practiced at home in the parades.

"We were drafted into the Dirty Dozen Brass Band," Davis claims. "We had nowhere else to go. I was practicing my horn seven hours a day, and then I'd go to an R & B or rock gig and only play a few lines. That got real dusty. We loved to play the street parades, but we couldn't get those jobs, because the older guys said we couldn't play 'Night Train' or 'Bongo Beep' in a traditional parade.

"So we said, hell, we're not getting those other gigs anyway, we might as well go out and play the tunes we've been rehearsing. And that made all the difference in the world. We convinced the Glass House to take a chance and put a brass band in a club, which was unheard of. Most of the older cats said we'd never make it, but we made it work.

"I remember six years ago we were playing 'Night Train' in the St. Joseph's Day Parade, and this guy came up waving his hands and making a big commotion. He said, 'You can't play that here!' The other day that same person called me up asking how to get some of these nightclub gigs. I told him, 'You must be kidding. You didn't need us then, you don't need us now.' " A big grin of satisfaction spreads beneath Davis' trim moustache.

The Dirty Dozen's persistence has paid off. Producer George Wein has made them a regular feature on his Kool Jazz Festival circuit. The Talking Heads' David Byrne acknowledges that his new brass band solo album, "Music for the Knee Plays," was inspired by the Dirty Dozen.

Ellis Marsalis, the patriarch of New Orleans jazz, insists that "the Dirty Dozen Brass Band is a good example of why the link to the past has never been broken in New Orleans jazz and never will be broken. It doesn't matter whether or not they play 'When the Saints Go Marchin' In.' What made the music was not the songs but the style."

"We don't try to copy the songs the way Bird or Miles did them," says Davis. "We know we have to get things from people who went before us, but we don't want to be copycats. We have to make music so people won't feel inhibited about getting up on the dance floor. 'Blue Monk' was a straight-ahead jazz number, but we turned it into a lowdown funky blues so people could dance to it.

"We did the same thing with Duke's 'Caravan.' The horns went ahead and played the tune, but the drums and tuba kept up that constant rhythm. We could have played it like Art Blakey, but it wouldn't have fit the crowd at the Glass House."