Stephen Sondheim's "A Little Night Music," cast with actors who sang or stabbed at singing on Broadway in 1973, has entered the repertory of the New York City Opera in a classy production, with singers who act very well.

Presented for the first time recently at the New York State Theater, it's probably the best of the hybrids the company has attempted. The voices all were good but never "too operatic."Sally Ann Howes, the second Eliza in "My Fair Lady" on Broadway, played the actress Desiree who gets to sing the show's best-known song, "Send in the Clowns." She did it with poignant musing, the way it fits into the plot.

Regina Resnik, from 1944 through '83 at the Metropolitan Opera and since then on Broadway in "Cabaret," played her mother, Madame Armfeldt. She has the best lines to speak and her timing and delivery were perfection. She did full justice to "Liaisons," her reminiscenses of affairs. Most importantly, Resnik was never vulgar.

The production is elaborate and highly effective, with many scene changes.

The plot, based on Ingmar Bergman's film "Smiles of a Summer Night," has many facets. Fredrik Egerman (George Lee Andrews) has a young wife (Beverly Lambert) and a son (Kevin Anderson) who loves the young wife.

His former mistress, Desiree, now is the mistress of Count Malcolm (Michael Maguire), whose wife (Maureen Moore) makes the most of the second-best set of lines.

There's a lusty maid (Susan Terry) who gets to sing "For I Will Marry the Miller's Son." And there's Desiree's daughter, looking like Alice in Wonderland and played with winning solemnity by Danielle Ferland.

It was an amusing idea to cast a count not only younger but a great deal taller than Fredrik Egerman.

We enjoyed this "A Little Night Music" more than its Broadway presentation. Because it has so many different couples and entanglements and different ages and levels of experience, it is easily compared with "Aspects of Love," now on Broadway. "A Little Night Music" seems real and wise and "Aspects of Love" seems more than ever to have been charted on graph paper.

The show has been scheduled for six performances in October.