PRESENTING a show with the full title The Seven Deadly Sins of the Lower Middle Class to a Cambridge/Loeb Drama Center audience risks a failure of communication: the gulf between Brecht's selfish characters clawing away at each other on the stage and the dainty gourmet shops sitting outside on Brattle St. seems wide enough to swallow Seven Deadly Sins' compact message. The great virtue of Alvin Epstein's American Repertory Theatre production is its dextrous explication of Brecht's easily garbled multiple ironies. Epstein uses his performers, music, dance, mime and even neon signs to illuminate Brecht's critique of the half-life of the bourgeoisie; he gives it such sober clarity that even the most plumped matron must follow Brecht point by point, and shudder.

Inverting the scheme of the traditional morality play, Brecht has his characters--a pair of sisters trying to earn money for their family home--avoid the traditional deadly sins so they can practice far worse ones more efficiently. One sister (both are named Anna) serves as guardian spirit to her suffering sibling: as they travel from city to city, climbing a ladder of fortune, the worldly temptations of Anna 2 are warded off one by her moralizing sister.

When Anna 2 as a dancer wants to show off her art, Anna 1 convinces her that if she wants to earn money she'd better show off her body instead. Later, as an actress, Anna 2 grows angry at her director's martinet-like behavior, but her sister explains to her that anger against injustice won't do for a girl who's trying to make it in the world. In the longest section of The Seven Deadly Sins, Anna 1 argues with and then manipulates her sister to prevent her from putting aside a rich lover for a poor but more truly loved one.

Ellen Greene's performance as Anna 1 is critical to the communicative power of the production: her clear enunciation and vocal power keep the words from getting lost in the bustle on stage. But she lacks the vocal or emotional resources to prevent her voice from becoming monotonous at times. I missed Carmen de Lavallade's Anna II (she is injured but expected to return to the show), but Julie Ince's performance in the role--which requires a sort of supine acceptance of the world, with vague but unquenchable rebellions continually flaring up--was only passively effective. Her dancing succeeded in showing that she was victimized, but not how victimization transformed her.

THANKS TO Michael Feingold's new translation and Epstein's careful attention to keeping the stage action intelligible, the upside-down Brechtian morality comes through without ever having to be explicitly stated. Given that most of the action is mimed or danced, and that the running commentary emerging from Anna 1 and the sisters' family chorus often states only obliquely just what the sisters are doing, that is a major accomplishment in the revival of this work.

The production also succeeds in recreating the detail of Brecht's fanciful vision of America as a Babylon on wheels. Sordid vulgarity falls from the garish costumes, the trashy props, and the giant neon arch--inscribed with the names of the seven sins lighting up in succession like a stage-wide slot machine that lands on whichever sins is being acted out below. In this world, beauty becomes a painted go-go dancer, so it's no wonder lust, pride and anger should seem more virtuous than the alternatives of self-denial, hypocrisy and quiescence.

As morality play and spectacle both, the A.R.T. production well serves this idiosyncratic work; it fails only on a final count. Brecht's aesthetic of the theater allowed for no catharsis; his works end by posing the question of the world to the audience and waiting for the answer. The fault does not seem to lie with anyone in particular--Epstein, the performers, or Gary Fagin's energetic conducting but somewhere towards the end of this Seven Deadly Sins an alchemical transformation fails to take place: the dilemmas facing the characters fail to become the dilemmas facing the audience. It understands them but feels no urgent need to make a choice.

PERHAPS THE MOMENT of transcendence missing from this production--the moment when the burden of action falls on the audience, not a purgation but a punch to the jaw--is sabotaged by the presence on the same program of another work, The Berlin Requiem, which, as presented, is so starkly untheatrical that it makes you feel uncomfortable merely to be sitting in the theater. Hastily substituted for two Samuel Beckett pieces at a late date, The Berlin Requiem is a series of seven songs devoid of light, hope, and in the end life itself. It is a work of music, really, not theater at all. Weill's orchestration turns the woodwind section into a mock organ, coldly pealing in the face of death.

Director Travis Preston, recognizing the work's nature, has staged the work simply by placing the three singers on a dark stage instead of at the front of a concert hall. The performance of the songs by Robert Honeysucker, David Ripley and Kim Scown is remarkably emotional for such somber music, and Honeysucker especially in the "Second Report on the Unknown Soldier" creates an affecting vocal performance with no need of a set of other theatrical assistance.

On its own, The Berlin Requiem presented on stage might prove a worthwhile experiment; but on a double bill it undercuts its competition, turning its audience from theater-goers into listeners. Between the stern, subterranean gloom of the Requiem and the moral topology of The Seven Deadly Sins, the evening of theater becomes oppressive--more oppressive than necessary, even to portray Brecht's oppression-filled world.