On the eve of his journey to Africa, Mayor Marion Barry couldn't have made a more appropriate entrance to his bon voyage party. Led by two local drummers, playing a spirited ceremonial song from Guinea, Barry paraded onto the patio of Meridian House, where 150 friends were trying to give him as authentic an African send-off as possible.

"How do you like our version of 'Hail to the Chief'?" kidded Herbert O. Reid, the mayor's counsel, who entered with Barry, his wife, Effi, and a half-dozen African ambassadors. The effort for a genuine African mood extended to the buffet of ground-nut chicken and cous cous and the going away gifts, a straw hat for Effi Barry, and a hand-dyed dashiki for Barry, who was once identified according to whether he wore one of the traditional shirst or not.

"I've tried to contain my excitement but I'm delirious," said Effi Barry, as the drums and conversation temporarily stopped. The Barrys leave this afternoon for a five-nation, 16-day tour, their first official trip abroad and their first visit to Africa.

The impact of this trip, agreed two veteran African specialists and one ambassador, went beyond the scheduled economic talk and presidential summits to simple visibility. "Sending a prominent American official to Africa further identifies our concerns with African interests," said Richard Moose, assistant secretary of State for African affairs. Paul Bonami, the Tanzanian ambassador, added, "The one important thing to establish is a rapport."

Rep. Charles Diggs (D-Mich.), a leading expert on Africa, said, "The impact can't be measured. The question of being there is just so important. I argued for Marion to go to South Africa and don't worry about the impact of the whites but think about the 80 percent blacks. You have no idea what just the presence can mean to them. They even tore my shirt off in the street." The Barrys will visit Liberia, Senegal, Kenya, Tanzania and Zambia.

Ambassador Timothee Ahoua, of the Ivory Coast, the dean of the African diplomatic corps, and said the ambassador's briefing of the Barrys stressed political and development issues. "I stressed economic development because I am sure every head of state will talk about economic exchange," said Ahoua. Barry expressed surprise at the warnings of the ambassadors that their countrymen would challenge the depths of concern of black Americans for African issues. "I hope to give a better feeling for what black Americans truly feel because it is a commitment," said Barry.

As the line for the buffet wound through two rooms of the elegant French townhouse, Barry was deluged with last-minute advice. Joseph Kennedy, director of international development of Africare, who returned from Kenya four days ago, said, "I told Barry one of the most exciting experiences would be witnessing Kenya after Kenyatta. It's a progressive experience." CAPTION: Picture, Mayor Marion Barry (right), by Ken Feil - The Washington Post