The Federal Jazz Commission, a New Orleans style group, played Dixieland while a line of enthusiastic dancers twirled their decorated plastic umbrellas.

For contrast and solemnity, the University of the District of Columbia Chtrale, dressed in long, gold-colored gowns, sang the Credo and Sanctus from Haydn's Mass No. 3.

The occasion was the dedication of two downtown pedestrian malls, constructed at a cost of more than $6 million and designed as a key element in the city's effort to revitalize the old central business district east of 12th St NW.

Mayor Walter Washington and other city officials joined about 300 citizens of all ages who seemed to enjoy the opportunity to take in the sun and listen to the music, if not the speeches.

The ceremony took place at noon on the Library Place Mall, on G Street between 9th and 10th Streets. The mall, built of granite and brick paving and closed to auto traffic, is framed by the modern glass and steel Martin Luther King Library on the north side and by a Federal City College building and the gothic style St. Patrick's School on the south.

A walkway with an intricate fountain and featuring recessed seating areas and dogwood and Bradford pear trees, runs down the length of the mall.

Mayor Washington, in a brief address, referred to fears expressed by some that the "Streets for the People" malls would attract undesirables.

"This is for good folks, mean folks, all sorts of folks," Washington said. "We're just going to have to live together and in harmony. This is what cities are all about."

Washington said that he hoped a proposed civic and convention center could also become part of the overall plan to bring people and businesses back to the central city.

Marie Bowen, a young unemployed woman, sat with a friend at the other end of the mall and said she thought the whole thing was a good idea.

"I think there's a lot of people who like to walk and like to see other people," she said. "The sound of the waterfall really knocks out a lot of the street noises."

City officials said they hope any financial losses suffered by store owners because of construction of the malls will now be recovered. Douglas Schneider, director of the city's departmetn of transportation, said parking in the area was adequate and expressed the belief that people will be willing to travel by Metro to shop.

"In the long run, the businesses will depend on our ability to get people into the area," said Lawrence Press, acting chief of the planning and research division of the city's housing department.

Nearby merchants who have waged a battle against the malls are not so sure. Their original intense opposition has dissipated somewhat, and the attitude of merchants interviewed yesterday appeared to be one of wait and see.

"We've got to see if this great transit system that we have is really going to produce and bring them down," said James Mangun, manager of George's, an appliance store on the second of the two new pedestrian malls know as Gallery Place Mall on F Street between 7th and 9th Streets.

Mangun said he has lost about 30 per cent of his business volume since construction began.

Nancy Hertz, who owns a card shop, is not optimistic that the Metro will bring people and business. "The only thing I get from Metro are people coming in here asking for change every night," she said. Hertz said her business volume had dropped 48.per cent since through traffic was cut-off from F Street.

A wide range of activities is planned on the two malls during the coming months, including noon concerts on Tuesdays and Thursdays and a Renaissance Fair next weekend. The fair will feature jugglers, acrobats, fortune tellers and music from that period. The musicians and performers will be in costumes, and handicrafts will be sold.