THE DUENNA, by Richard Brinsley Sheridan; adapted and composed by Lance Mulcahy; directed by Garland Wright; scenery and costumes by Desmond Heeley; lighting by Frances Aronson; choreography by Randolyn Zinn; with Lance Davis, Henry J. Jordan, Brent Barrett, Mary Elizabeth Mastrantonio, Lu Leonard, Gordon Connell, Betsy Beard and Joel Kramer.

At Center Stage, Baltimore, through Jan. 16.

Between the Folger Theatre and Baltimore's Center Stage, a regular Richard Brinsley Sheridan festival is underway. "The Rivals" and "The Duenna" represent, in fact, nearly a third of the Sheridan oeuvre, the author having abandoned playwriting for politics in 1780, after just a few years of concentrated output.

"The Duenna" is an operetta, with music originally by Sheridan's father-in-law, Thomas Linley, and now by Australian-born Lance Mulcahy, who has also adapted the text. Mulcahy wrote his score a few years ago and, as he explains in a program note, had great difficulty getting the adaptation staged. "It reads as a rather silly little thing," he says, "but it just happens to work extremely well in musical theater."

This is a grand claim, but unsupported by the present evidence.As unveiled Tuesday night in Baltimore, "The Duenna" is indeed "a rather silly little thing" which utterly vindicates the judgement of all the nameless producers who must have failed to see what Mulcahy saw in it. If there is a level of deft performing that would substantiate his claims, it must be a level several levels higher than that achieved here. And director Garland Wright and his cast have so liberally camped up the whole enterprise -- with exaggerated poses and gestures and extraneous little gags -- that even their faith in the project may be questioned.

Mistaken identity is at the heart of "The Duenna," as it is at the heart of "The Rivals." Don Jerome, a wealthy citizen of Seville, wants to marry his daughter off to the rich, ogreish Don Pedro. She, having other ideas, runs away with her impoverished lover, Antonio, and leaves the old family duenna behind to impersonate her and receive Don Pedro's advances. The ruse is sustained so adroitly that not just one but three pairs of lovers are united in the end.

The tangles of the plot are funny. Not much else is. Each of the eight members of the cast has his own little comic schtick (and the protean Lance Davis has four schticks, for his four parts). But it takes only a few minutes to exhaust the variations within each performance. As the dour Ferdinand, for example, Henry J. Jordan gets a good laugh the first time he assumes his statuesque swordfighting posture with his free hand flamboyantly curled over his head -- but by about the fifth time it has become more annoying than amusing.

The acting is so consistently in this vein that it would probably be a mistake to draw any conclusions about the individual actors -- except that Brent Barrett and Mary Elizabeth Mastrantonio (who have been playing Tony and Maria in the Broadway revival of "West Side Story") are fine singers, and Mastrantonio probably puts up the firmest resistance against the general drift to camp.

As for the music, Mulchay has done an admirable job of re-setting Sheridan's songs, and his five-member orchestra (bass violin, violin, bassoon, flute and, in lieu of harpsichord, poly-Moog synthesizer) is a small pleasure to listen to. But the lyrics themselves are so abrupt and crudely constructed as to virtually foreclose the possibility of any subtlety or complexity in the misic; just when a melody threatens to get interesting, it starts repeating itself.

The most appealing aspect of this production, unequivocally, is Desmond Heeley's set, with its two arrow-slinging cupids overlooking the action and, in the background, its minitature profile of the tile rooftops of Seville. If scenery could sell tickets, this production would run forever.