At Columbia Road and 18th Street NW, the heart of Washington's most varied neighborhood, the Starlite Orchestra jazz band started a medley of Count Basie's "One O'Clock Jump" and Harry James' "Two O'Clock Jump."

On the other end of a mass of humanity, at Columbia and Kalorama Roads, the Jamaican reggae band "Spliff" broke into a wailing ballad about a beautiful woman who lived in the fast lane, using heroin and cocaine.

Squeezed in the middle, at Columbia Road and Mintwood Place, the Latino band Los Gitanos cried out with a salsa-flavored version of Pink Floyd's "The Wall."

It was all happening at high noon yesterday: Adams-Morgan Day. And what better way to celebrate, in this bastion of ethnic diversity, than with a battle of the bands?

With clear skies and temperatures in the 80s, the day was a classic prelude to autumn in Washington, that season when the days are warm and the nights cool and romantic.

Last weekend, the action was in Southwest at a crab feast along the waterfront, with crabs, jumbo shrimp and juicy oysters -- all you could eat. On Saturday, there was a jubilee in Georgetown and a harvest festival along Georgia Avenue. But yesterday's celebration seemed to draw from the best of the rest.

Oil drums, split in half and set on sawhorses, were filled with charcoal and covered with mesh wire to form huge barbeque pits along Columbia Road, which was cordoned off for the day. White, spicy smoke billowed towards the rooftops as slabs of pork ribs, hamburgers, hot dogs and beef tips were thrown on top.

From embroidered tablecloths were served the foods of Central America, whose immigrant population now claims a sizeable percentage of Adams-Morgan's 30,000 residents. There were burritos from Mexico and Jumpin' Jackson meat pies and pelau (rice and peas) from Jamaica. There was fried codfish, fried bananas, French fries and fried chicken.

"Tender beef strips marinated in a distinctive sauce then sauteed with pepper, onions and zesty spices," read one sign attached to a sizzling grill.

Said the man, just in from Cuba, with the meatfork: "Meat, tree dolla."

There were politicians in evidence, as well: Practically all of the contenders in Tuesday's D.C. primary elections planned to drop in at the festival at some point during the day.

This was the fifth annual Adams-Morgan Day and, many said, the most delectable to date.

"Five years ago, there were some in the community who thought this was going to be a ripoff, with the underlying motive being just a way for businessmen to make more money," said Carol Davis, an employee of the American Psychiatric Association and an Adams-Moragn resident since 1968. "Now people see that this is a celebration of our survival as a neighborhood, that this is not a scary place, and people can get together and have fun."

Said Hal Wheeler, owner of the Columbia Station restaurant and chairman of the Adams-Morgan Day committee, "This is a day when the most ethnically diverse and most politically active neighborhood in the city shows that, despite hard economic times, we can put our differences aside and party."

There were many booths along the way offering arts and crafts -- a tribute to the estimated 1,000 artists who live in Adams-Morgan.

At the City Garden Co-op, the speciality of the day was "nonviolent food" for a "nonviolent world." A bumper sticker attached to the health food booth urged customers to "Love animals. Don't eat them."

Since the early 1950s, Adams-Morgan has been the city's principal port of entry for immigrants. The waves of newcomers can be roughly measured by the shops and restaurants that line Columbia Road from 16th Street west to Connecticut Avenue: Cuban, West African, Middle Eastern and Central American.

During the 1960s the neighborhood became something of a Bohemian hangout, a hippie retreat. The riots that culminated that decade left Adams-Morgan with its most serious test of race relations and cultural tolerance since 1954 -- the year when students at the black Morgan elementary school, then located at 18th Street and Florida Avenue NW, began attending the predominately white John Quincy Adams elementary school, which was located a few blocks away at 19th and California Streets NW.

In the 1970s, real estate speculators invaded. Was urban renewal a slick phrase for urban removal? In Adams-Morgan, the battle lines were drawn.

"The community was able to come together and deal with the developers on this question," Davis recalled. "Through all of the changes, we have nurtured some unity. And we have succeeded in keeping many of the people here who make a difference. We have learned that you can't stop change, but you can control it."

Adams-Morgan now has a community development corporation made up of the area's top 25 neighborhood groups. The corporation recently secured a $150,000 grant from the city's Department of Housing and Community Development to formulate proposals for increasing low- and moderate-income housing in the area, according to Jim Vitarello, who is chairman of the CDC economic committee.

Said Ramberto Torruella, a dressmaker who has lived in Adams-Morgan for 38 years: "The area has really come of age. I call it the new Georgetown."