Stage: Doonesbury

By Frank Rich

THE qualities that have made Garry Trudeau's comic strip ''Doonesbury'' a national treasure are all present in the musical-comedy version at the Biltmore Theater.  You'll hear the offhand dialogue that snares the self- contradictions of college kids of the 1960's.  You'll find some sly political jokes aimed at targets as ideologically diverse as William P. Clark and Jane Fonda.  Best of all, you'll notice that the tone of Mr. Trudeau's work is intact: on stage, as in the strip, Mr. Trudeau speaks in a sweet voice that lifts him well above the madding crowd of diurnal satirists.

The more literal specifics of the newsprint ''Doonesbury'' have been preserved as well.  Jacques Levy, the director, has engaged young performers who not only look exactly like the members of Mr. Trudeau's Walden Puddle commune but also sound just as we always imagined they would - even when they sing.  Peter Larkin and Patricia McGourty, the set and costume designers, have done a clever, light-handed job of duplicating the spirit of Mr. Trudeau's airy funny-pages doodling.

No wonder, then, that ''Doonesbury'' is a pleasant show.  The surprise is that it's dull.  A few bright interludes notwithstanding, this musical never catches fire.  Some of the shortfall can be traced to conventional failings of craft in Mr. Trudeau's book and a weak score by Elizabeth Swados.  There is also a philosophical problem.  Aren't we all, Mr. Trudeau included, getting a bit tired of watching 60's-style students as they beat a hasty retreat into the big chill of the middle-class mainstream?

Mr. Trudeau seemed to acknowledge as much when he suspended his comic strip early this year.  After more than a decade, he and his many imitators (on and off the funny pages) had said all there was to be said about such archetypes as Zonker, the spaced-out tanning-fanatic from California, or Mark, the hipper-than-thou disk jockey.  In his book for the musical, Mr. Trudeau wants to be done with these characters altogether: the show's premise places the Walden crowd on the eve of graduation, as they venture into the real world seeking jobs and mates.

Because the commencement exercises don't occur until the final scene, Mr. Trudeau must invent other story twists to fill up the evening.  Zonker's uncle Duke - a recreational drug enthusiast originally inspired by the journalist Hunter Thompson - conspires to bulldoze the students' off- off-campus house and replace it with condominiums.  Mike Doonesbury awkwardly tries to court the feisty J. J., and J. J. tries to come to terms with her long-lost mother, Joanie Caucus.  Yet the plotting seems perfunctory, as if the author is only killing time while waiting to bid everyone adieu.

Many of the book scenes are enervated rehashes or continuations of old strips.  The show's flimsy structure only accentuates its warmed-over feel.  Mr. Trudeau is torn between writing a standard musical-comedy narrative (complete with mawkish resolutions) and a series of sketches, with the result that neither form is realized. (For some reason the punchlines that precede the blackouts are the flattest in the script.)  Only the straight political gags have bite.  At various arbitrary times - but not enough times - a cartoon White House suddenly descends and we laugh heartily at the topical, piped-in lines that Mr. Trudeau has given to our incumbent President.

Oddly enough, Mr. Trudeau's song lyrics, his first ever, are far better than his book; perhaps the tight discipline of comic-strip writing has provided him with the miniaturist's discipline required.  In the funniest (if most irrelevant) song, a preppie chanteuse named Muffy declares, ''I love Nancy Reagan / I love Ronnie, too / What a pity their money is so new.''  It's too bad that Miss Swados accompanies such words with merrily intentioned but mostly flavorless music, wanly played by an on-stage, synthesizer-laden four-man band.  ''Doonesbury'' cries out for a score by Randy Newman - or, failing that, one with the zip of such Broadway progenitors as ''Bye Bye Birdie,'' ''Grease'' or ''Hair.''

Margo Sappington's choreography is as minimalist as the music.  But Mr. Levy's efficient staging and lively cast keep the show moving, however vague its destination.  With the exception of Gary Beach's vastly oversold Duke and the nondescript contributions of Lauren Tom (Duke's Chinese sidekick Honey) and Barbara Andres (Joanie), the performers could not be better.  They include Ralph Bruneau and Kate Burton as the haltingly lovesick Mike and J. J., Keith Szarabajka as the football-crazed B. D., Albert Macklin as Zonker, and Reathel Bean as the most fatuous ABC-TV newsman ever to appear on ''30/30.''  That fine actor Mark Linn-Baker does as well as possible by Mark, whose big song is especially lackluster.

In a class by herself is Laura Dean, as the blond cheerleader Boopsie.  ''I Can Have It All'' is the title of her solo turn, and this performer does have it all: she is a charismatic singer, dancer and comedienne who is good- naturedly sexy without ever becoming a stereotype.  Watching her, we remember how sweetness and sharp humor came together to ignite ''Doonesbury,'' the comic strip.  ''Doonesbury,'' the musical, too often seems pale by contrast: the Walden gang has finally grown up, and, as Mr. Trudeau might pejoratively put it, mellowed out.

Into the Real World

DOONESBURY, book and lyrics by Garry Trudeau; music by Elizabeth Swados; based on ''Doonesbury'' by Mr. Trudeau, by permission of Universal Press Syndicate; choreography by Margo Sappington; directed by Jacques Levy; scenery designed by Peter Larkin; costumes designed by Patricia McGourty; lighting designed by Beverly Emmons; sound designed by Tom Morse; orchestrations by Miss Swados; arrangements and musical direction by Jeff Waxman.  Presented by James Walsh, in association with Universal Pictures.  At the Biltmore Theater, 26l West 47th Street.