Strains of "Swan Lake" and "The Firebird" mingled with disco music at the Fort Dupport ice rink yesterday as world and national figure skating champions practiced for tonight's exhibition performances at Capital Centre at 8.

As photographers and television film crews crowded aroungt the rink, the potential medalists in the 1980 Olympics willingly obliged requests for "just one more of those" and, incredibly, "could you do htat in slow motion?"

No problem, said Rubin Huron, coach of the 20-member World Figure Skating Tour making the rounds of 15 cities in 21 days.

"Say, Frat, would you do a nice camel spin where you tuck into a split spin and into a split spin and into a layback again?" Huron asked Linda Fratianne, who executed the maneuver perfectly.

Fratianne, 17, a ballerina on ice, is considered the country's strongest contender for the individual women's gold at Lake Placid. She was both the U.S. and World's Ladies champion in 1977; the U.S. Ladies champion in 1978 and the silver medalist in last month's world championships at Ottawa. She lost the world championships at Ottawa. She lost the world title to Anett Poetzch of East Germany, also appearing tonight.

Unlike the world championship competitions the exhibition tour frees the skaters from performing compulsory moves, allowing them complete freedom in choreographing routines. As a resutl, they present a greater variety of flips, jumps and spins.

That freedom is evident in reigning British men's champion Robin Cousin's routine, which now includes a razzle-dazzle disco number that would shame John Travolta.

"I've always done ballet numbers and thd disco music is such a contrast," said Cousins, 20, considered one of the most interpretive skaters in the world today and who does his own choreophy. "I love to go the discos and this sort number has never been done before (on the ice) so I though I'd try it."

Cousins won the Bronze medal in last month's world men's competition. Gold medals Charles Tickner of the United States and Silver medalist Jan Hoffman of East Germany also will perform tonight.

U.S. pairs champion Tai Babilonia and Randy Gardner. third in the world pairs competition, amazed wobly-ankled novices yesterday with acrobatic movements and tongo dance routine.

Gardner, 20, is a freshman attending the University of Southern California on a part-time basis so he can arrange classes an courses to permit the pairs' grueling practices from 6:30 a.m. to 2 p.m. daily. Babilonia, 18, a high school senior, wants to attend USC so that their skating partnership won't be disrupted.

"We don't date each other," Gardner says. "We're more like brother and sister."

"Right now, what we're concerned about is keeping going until 1980 and then see what happens. Our goal is lake Placid," said Babilonia.

U.S. dance champions John Summers of Vienna and his partner Stacey Smiths also will be appearing.

Irina Rodnina and Aleksandr Zaitsev, the world's pairs champion from the Soviet Union, also will be performing. A husband and wife team, they have won the Olympic gold twice and she, with a former partner, has won the world championship 10 times. The record ties her with Sonja. Henie's 10 individual world championships.