It is too bad that Elizabeth Taylor is not a singer. Last year, her presence in the production of Lillian Hellman's play "The Little Foxes" helped to break box-office records on two continents. Last night the same play, in Marc Blitzstein's operatic revision, "Regina," played to hundreds of empty seats at Wolf Trap.

This production needs a symbolic figure of Taylor's power to sell tickets, and that is almost all it needs -- though a really good opera house to shelter the performance would be a blessing.

The Wolf Trap production would be outstanding in any case. Last night's voices, particularly those of Jane Williams, Virginia Boomer, Robert Serrier and Philip van Lidth de Jeude, were equal to or better than those of the New York City Opera production that is preserved on CBS Records. The difference was spectacular in the case of alto Anita Berry, the only one of these singers who will be repeating her performance tonight.

Considering the circumstances of this production -- given in a tent not designed for music, on a stage not very suitable for opera -- the achievement is amazing: a triumph of mind over matter, of talent and determination over disheartening conditions.

The voices are served by a production that is thoughtful and well-executed in all other respects. The single set, with high ceilings, Greek columns and lots of red velvet drapes, represents a southern mansion with fine precision. It is filled with stage movement, presumably the work of choreographer Frances Smith Cohen, that brings the action vividly to life -- notably in the choral tableau that opens the party scene in Act II.

"Regina," unlike "Trovatore" or "Rigoletto," is an opera that tends to work dramatically and theatrically if the show is to have any impact at all. The music is seldom of the show-stopping, stand-alone variety that can make an audience forget about everything else. And the plot, dealing with fraud, theft, a curious kind of violence and smoldering family hatred, is more complicated than opera plots usually are or should be. Adelaide Bishop's stage direction made the intricacies of this plot crystal clear without ever slowing down the action, and her coaching brought out considerable acting ability throughout the whole cast.

Music director Richard Woitach conducted a well-pitched, excellently balanced performance. In the absence of a regular pit, the orchestra intruded visibly on the stage; Woitach could be seen conducting with much of his body above stage level, and the double basses and harp also came up into the audience's line of vision.

But once the performance got rolling, these distractions seemed to become invisible; the eyes focused on the interesting things that were happening on the stage, and the musicians were able to do their work unnoticed. The orchestral sound, too, was present and powerful put unobtrusive, supporting the voices but never covering them.

There will be eight major cast changes in tonight's single repeat performance, to give other young singers a chance at the spotlight. If tonight's cast is anywhere near the equal of last night's, Wolf Trap has assembled a truly amazing group of young singers for this summer's opera company.

"Regina," in the past, has been something more than a play set to music, but perhaps something less than a full-fledged operetta in the traditional sense. We might call it an almost-opera, a uniquely American kind of musical theater. It stands near the beginning of a tradition that now includes "West Side Story," "Sweeny Todd" and "Willie Stark." Our reluctance to call these works operas may be based partly on the kind of voices some of them use and the relative complexity of the music, but I think it is also rooted in a subconscious feeling that real operas must reflect the speech patterns and musical idioms of Italy, France or Germany.

"Regina" is completely American, and if that means occasional echoes of ragtime, jazz and even Tin-Pan Alley, so be it. Perhaps it is time we began to recognize a different kind of opera as a legitimate form of American art. In "Regina," the music works; it works particularly well in this production, for which Woitach has done some very judicious trimming.

One reason it works is its ability to reflect the varieties of American speech. And it often works in relation to the spoken as well as the sung dialogue. The music is used most often not for vocal display but to pace, to accent and to strengthen the drama. Often, it is used as melodrama in the original sense of the word: spoken dialogue supported by orchestral accompaniment. The effect is very powerful at some of the opera's key moments.

The title role, ideally, could use a singer like Maria Callas to portray the magnolia-scented Lady MacBeth, who is the mainspring of the plot. Last night, Jane Williams was vocally magnificent, particularly at the beginning and end of Act II, and her slightly understated acting complemented her singing effectively. Robert Ferrier was equally effective in the role of her husband, and his climactic death scene was probably the most memorable moment of the opera as it is of the play.