Society orchestra leader Peter Duchin, 48, was married Christmas Eve in Stowe, Vt., to writer and longtime companion Brooke Hayward, also 48, a union that might not have been greeted with the greatest of joy in the home of Averell and Pamela Harriman. Duchin is the son of the late society orchestra leader Eddy Duchin and society figure Marjorie Oelrichs. After his mother's death, Duchin grew up in the Harriman home while his father was in the Navy during World War II. In recent years, there have been tensions between Duchin and Pamela Harriman, according to an old friend of Duchin.

In a strange coincidence that adds to the tensions, Hayward's father, the late producer/agent Leland Hayward, was once married to Pamela Harriman, who was not portrayed in a flattering manner in Brooke Hayward's autobiography, "Haywire." The book was an account of Hayward's unhappy childhood and two failed marriages, including one to actor Dennis Hopper.

Leland Hayward had been one of the most important Broadway agent/producers of his time. His clients included Ernest Hemingway, Greta Garbo, Judy Garland and Fred Astaire. He also produced such Broadway hits as "Call Me Madam," "South Pacific" and "Mr. Roberts." Brooke's mother was the actress Margaret Sullavan, who starred in such films as "The Shop Around the Corner" and "Only Yesterday." In the complicated world in which Brooke Hayward grew up, her mother had once been married to Henry Fonda, who was one of Leland Hayward's clients. Duchin frequently comes to Washington because his four children from a previous marriage live here. He will be in town next week bringing in the New Year at the Jefferson Hotel, and Brooke Hayward is expected to be with him. New Year's Around Town

It may not be Times Square, but it will be New Year's Eve again at the Old Post Office Pavilion with entertainment inside and outside. Outside will be James Brown, Experience Unlimited, Willie Colon, the Del Fuegos and On Beyond Zebra. Inside will be Cab Calloway, the Dirty Dozen Brass Band and D.C. Jazz Workshop. At midnight, with Mayor Marion Barry doing the countdown, the big postage stamp will fall and the Grucci fireworks will go off.

Elsewhere around town: There will be waltzing in the Kennedy Center Grand Foyer after the Concert Hall and Opera House performances; at the Departmental Auditorium the Young Friends of the Red Cross Ball will feature "fractured fairy tales" with even the food on a fairy-tale theme, whatever that is.

The glitter will be at the hotels, from the above-mentioned Jefferson to the new Grand Hotel (formerly the Regent), where the theme is the movie "Grand Hotel." For $350 a couple there, it will be continuous showings of the film, '30s and '40s music, dinner, a night in the hotel and a champagne brunch. The Mayflower will host a Diamond Ball in honor of the Mayflower's 60th year of uninterrupted service. At the Four Seasons for $225 a person there will be dinner and a stage show "reminiscent of the 1940s" to benefit the USO. At the Capital Hilton, the Washington Beethoven Society will hold its second Fledermaus Ball, which re-creates a prince's palace in Vienna. The attire is white tie and ballgowns, and ladies are told to wear eye masks. But then there's always popcorn, classic Coke and Dick Clark at Times Square in New York City. Cheaper and saner. End Notes

After 15 years of Project Harvest, a Christmas food drive, Lillian Green, the founder of the drive, will be honored Sunday at a jazz benefit at Celebrity Hall on Georgia Avenue. Rep. Walter Fauntroy will present her with an award, and proceeds from the event will go to the United Black Fund, Mothers Against Drugs, Park Warden Projects and the Black Man's Development Center . . .

The Royal Society for the Prevention of Cruelty to Animals has launched a campaign against an upper-class British tradition of horse riders and a pack of dogs thundering across the countryside in quest of one fox for the hounds to rip to pieces. The RSPCA spokesman said the majority of Britons consider fox hunting "barbaric." Many Americans feel that way also, but there are also people on this side of the Atlantic who enjoy chasing one small animal with several horses and a large pack of hounds . . .