Victor Borge, who conducted the National Symphony Orchestra from time to time last night, has at least one essential talent of a conductor: a sense of timing. He shows it with his voice as well as his baton, in the way he announces, "We will play the Overture to 'The Barber of Seville,' by . . .long pause with puzzled look on his face by all means." Or the way he tells latecomers, "Sorry you missed that one . . . short pause We will play it again . . . long pause with much laughter tomorrow." As a matter of fact, he will tonight, but you may have trouble getting tickets.

His conducting of the Intermezzo from "Cavalleria Rusticana," a Franz Lehar medley with piano, the "Voices of Spring" Waltz and Schubert's "Ave Maria," left many aspects of the conductor's art unexplored--large-scale architectonics, for example, and the more refined subtleties of phrasing and dynamic nuance, not to mention the art of Luftpausen (which could have been used) and the entire, convoluted field of baroque Auffu hrungspraxis (which could not). But he also included two Scandinavian works of some substance: Sibelius' "Finlandia" and the "Dance of the Cockerels" from Nielsen's "Maskarade," a brisk, colorful number that involves some tricky rhythms and changes of pace.

His interpretations of this music were free of notable eccentricity, his baton technique was better than that of many conductors with large reputations, and he set good tempos and kept the sound well-balanced. There was no playing to the audience during these serious moments, though there was plenty in the comic routines, which made a very long program seem very short.

Borge is clearly enthralled with the waves of sound that ensue when he twitches his baton and is willing to make jokes in return for that pleasure--plus a substantial and well-earned fee. He probably could have become a noteworthy conductor -- one of a large crowd -- but the accidents of his biography have made him the only one of his kind. It is probably better this way, but his manner on the podium hints that sometimes he dreams of other possibilities. And Jimmy Durante probably wanted to play Hamlet . . .