An overflow crowd at the Renwick Gallery gave the fifth annual City Dance festival an appropriately euphoric welcome yesterday afternoon, as the Murray Spalding Dance Theatre presented the official opening performance.

Once a year, the festival focuses public attention on the diversity and vitality of dance in the metropolitan area with a binge of events. City Dance '81 is taking the festival name even more seriously than its predecessors, by spreading the action across sundry areas, spaces and times. Free daytime appearances yesterday and Monday by the Virginia Jazz Theatre and the Turkeys on the Run Cloggers, as a sort of curtain-raiser, already carried the festival banner to the Mazza Gallerie on upper Wisconsin Avenue. Yesterday's Renwick program staked out yet another site, and there are more to come.

Seeing the Spalding troupe at the Renwick rang some poetic chimes -- one of the two Spalding offerings, "A Fine Romance," was created for and had its premiere in the Renwick's Grand Salon in 1978. The furnishings of the place, which include plush velvet love seats, heavy drapes and carpeting, inlaid chests and luxurious bric-a-brac, as well as wall-to-wall paintings, make a splendid setting for this choreographic bouquet to the '30s ballroom era.

Dressed to the nines in black and white formals, Spalding, Eric Hampton and Victoria Hileman sweep, swoop and dip their way through a medley of period tunes, including such Astaire-Rogers vehicles as the title song and "Night and Day." The three enter separately and then dance in every possible pairing, as well as solo, before their grand collective exit. The sexual ambivalence of Spalding, who's in white satin tails and dances opposite both Hampton and Hileman, is an inspired touch of mystery that helps to darken, and hence deepen, the nostalgia of the piece.

Mary Giuici joined the other three dancers for "The Doubtful Guest," the opening Spalding opus, which wasn't created for the Renwick but by happy coincidence might well have been, given the women's high ruffled collars and the generally "old-fashioned" air of the work. Danced both to piano music by Chopin and the whimsical poem by Edward Gorey which gives the piece its name, "Guest" is on the coy side, but the performers delivered it with disarming tact and gusto.