Despite the threat of a downpour and the muggy weather, what looked like close to 5,000 people turned out last night at Wolf Trap to watch the American Dance Machine parade its potpourri of dance numbers from Broadway musicals. And to judge from the whooping response of the crowd, a good time was had by virtually all. Can there be anything to complain about?

No, and then again, yes. As entertainment, ADM seems to have found a sizable and appreciative audience, and it clearly gives them something they crave. Nothing to quarrel about here. As an artistic venture, however, the troupe continues to raise almost as many questions as it answers. ADM was founded in 1975 to preserve and perpetuate the rich dance heritage of American musical theater, which in many ways has been an endangered choreographic species. The "scholarly" sides of ADM's activities -- research, restoration, recording, teaching, archiving -- are of unquestionable value.The performance aspect, though, has been and remains loaded with problems.

In last night's program, for instance, it was a pleasure to see such flavorful, original and quintessentially American dance inventions as the numbers from "George M.," "Cabaret," "Half a Sixpence" and "Brigadoon," displaying the varied choreographic signatures of Joe Layton, Ron Field, Onna White and Agnes de Mille. But the better the choreography, the more one is bothered by seeing such work excised from dramatic context, shorm of apt decor and atmosphere, and sung and danced by performers who can neither duplicate the charisma of the originators, nor, in many cases, adequately approximate the style or spirit that enlivened this material at birth.

Then there are the mediocre items -- novelty numbers, trifles and just plain second-rate fillers -- that make one wonder what is worth preserving in the name of history and what isn't. There are technical problems (why do a clog dance if you can't do it on a percussive floor?) and conceptual ones, for example: What do the highly stylized exhibition numbers on last night's bill have to do with the social dance forms they are supposed to exemplify? Or with musical comedy?

Wayne Cilento is an assured Broadway veteran and Christine Sarry is a fine ballet dancer, but the two of them as headliners and their reasonably proficient colleagues didn't add up to the dynamite personalities that musical theater thrives on. The evening's one authentically "historic" performer -- jazz tapper Harold "Stumpy" Cromer -- was rather ingloriously tacked on to the show as a curtain-raiser, without accompaniment or proper flooring. In sum, there's much cause for ambivalence: One is grateful for ADM's noble conservation effort, but skeptical of many of the hows and whys.