A DAY IN HOLLYWOOD, A NIGHT IN THE UKRAINE, a musical with book and lyrics by Dick Vosburgh; music by Frank Lazarus; directed and choreographed by Tommy Tune; co-choreographed by Thommie Walsh; scenery by Tony Walton; costumes by Michel Stuart; lighting by Beverly Emmons; produced by Alexander H. Cohen and Hildy Parks.

With Priscilla Lopez, David Garrison, Frank Lazarus, Stephen James, Peggy Hewett, Kate Draper, Niki Harris and Albert Stephenson.

At the Mechanic Theatre, Baltimore, through April 19.

What could be more delightful than to discover a long-lost Marx Brothers movie -- one so rarely shown that even the brothers, were they alive, might not remember it?

"A Night in the Ukraine," it is called, and it opened Tuesday night at Baltimore's Mechanic Theatre on its circuitous path from London to New York. The impersonations of Groucho, Chico and Harpo are merely brilliant, not actually uncannny. But the script and score follow the Marx Brothers rhythms (one could easily have said "inimitable" rhythms) with astonishing accuracy. Author/lyricist Dick Vosburgh and composer Frank Lazarus haven't missed a preposterous beat.

"Tell me, has anyone in your family ever committed suicide?" asks David Garrison as Groucho, of Lazarus as Chico.

"I no think so," says Chico.

"Well," says to Groucho, "why don't you go down to the Volga and break the monotony?"

In the same vein -- is there any other? -- Groucho asks: "What do you call yourself?"

"I no call myself," replies Chico. "I'm always near."

In song as well as story, "A Night in the Ukraine" is the real McMarx. One lyric rhymes "peroxide" with "dockside." In another, Groucho announces himself as one "Samovar the lawyer" who "wouldn't know a legal book from a copy of 'Tom Sawyer.'"

There are people, one hears, who do not find the Marx Brothers irresistible, and it is a fair guess that they won't find an imitation irresistible, either. What is far more surprising to discover is that even a certified, commitable fan -- oneself, for example -- can tire of prolonged neo-Marx Brothers nostalgia, no matter how well executed. "A Night in the Ukraine" includes deft takeoffs on the romantic as well as the farcical aspects of its Marx Brothers models, but here admiration merges with exhaustion. The allure of parody vanishes when the parodists have no critical point to make, no goal except to simulate the original as closely as possible.

There is another half to the concoction now occupying the mechanic stage. It is called "A Day in Hollywood," and it is a singing, dancing, smiling Marxless musical revue ostensibly performed on New Year's Eve 1939 by the ushering staff of Grauman's Chinese Theatre. The songs include a rich assortment of '20s and '30s kitsch, with special attention to the works of composer Richard Whiting, author of "Louise" and "Hooray for Hollywood." "A Day in Hollywood" also introduces a daring and funny choreographic innovation -- a duplex stage with a second-story level of dancers visible only to their thighs.But otherwise, the nostalgia-to-humor ratio is far higher in this half of the show, and the result far less entertaining.

It is high time nostalgia became a means rather than an end. The people involved in "A Day in Hollywood/A Night in the Ukraine" (notably Vosburgh, Lazarus and a fine singer/comic named Priscilla Lopez, one of the original "Chorus Line" cast) are talented folks -- way too talented to be expending their gifts this way.