Vibrant theater in Boston

There's an old saying that used to run around the theater. At any given time, somewhere in the country, two or three directors would sit around saying, ''If we could start a resident professional company in a city that didn't already have one, where would be the likeliest place?'' And they'd always say, ''Boston.''

- Huntington Theatre Company producing director Peter Altman

That old saying should pass into the large body of theater folklore. This ''likeliest place,'' a metropolitan area containing 3 million people and 60 universities, which had been without a high caliber mid-sized theater since 1970 , now has three.

The work they're doing ranges from reliable standards to daring innovations. Two of their shows, ''Mother Courage and Her Children,'' at the Boston Shakespeare Company, and ''Moon for the Misbegotten,'' at American Repertory Theatre (ART), have received national attention.

They've all had successful seasons. When ''Cyrano de Bergerac'' was running at the Huntington Theatre Company concurrently with the two hits above, all three theaters were sold out simultaneously. ART has played to 94 percent capacity; Huntington to 75 percent; Boston Shakespeare Company has done less well with an average of 50 percent. More than 180,000 people saw their shows this year.

And none of these theaters is over five years old.

At this point the three are finding their footing, their vision, and their voice. Each adds strikingly different threads to the fabric of Boston theater.

American Repertory Theatre, Cambridge

''We seek imaginative, poetic new American plays,'' says ART's artistic director, Robert Brustein. ''It's a mistake to labor under the shadow of another country, even Britain. We're a country with culture and style, we want to develop that and use it on stage.

''And we don't limit ourselves to new American plays; we're always on the lookout for little-known classics whose time is come. We believe in plays that have both emotional power and intelligence.''

For the most part, ART fulfilled that vision this year. The company presented ''Big River: The Adventures of Huckleberry Finn,'' ''Traveler in the Dark,'' by new American playwright Marsha Norman, and Eugene O'Neill's ''Moon for the Misbegotten.''

Although directed by an Englishman and acted by a Canadian and an Englishman, O'Neill's uniquely American vision was beautifully portrayed.

The company has also presented ''Measure for Measure'' and Pirandello's ''Six Characters in Search of an Author.'' All were critical successes except for ''Measure'' and ''Traveler.''

A professional company in residence at Harvard's Loeb Drama Center, ART came here in 1979 from its home at Yale University, where it had been under the helm of Mr. Brustein since 1966.

One of ART's strengths is that it is the only one of the three with a permanent company of actors that do shows in repertory. Actors who work together in repertory gain security, flexibility, and intuition about one another that makes for richer acting - and ART's are no exception.

The university connection gives the company a modern 550-seat theater and state-of-the-art technical equipment. Their shows tend to have spare, movable sets and intricate technical effects, like creating the effect of an entire room through the use of lights and a scrim in ''Six Characters.'' Such effects are used but not flaunted; they take a back seat to the generally powerful acting.

ART is committed to taking its theater to the world. It's pedaling its wagon this summer to the Los Angeles Olympics Arts Festival and the Quebec International Theatre Festival. It will take its current hit, ''Six Characters, '' as well as two revived productions, ''School for Scandal'' and ''Sganarelle.'' The last play, originally directed by Andrei Serban in 1978 at Yale, has toured several times and has been taped for British television.cho

ART also presents a Monday evening series of films, poetry, and letters that relate to whatever is currently showing.

Huntington Theatre Company

Affiliated with Boston University and housed in a comfortable wooden theater built in the 1920s, the Huntington Theatre reeks of classics.

The company's aim, says producing director Peter Altman, is to present a ''variety of classic and modern plays of the best possible quality in the spirit in which they were intended; we want to fulfill the vision of the writers. We also want to do plays that haven't been seen here ever or at least not recently.''

The Huntington's role in this tripod of theaters is provider of accessible, solid, standard productions. Its productions tend to be visually beautiful, faithful to the text, conceptually conservative, and modestly acted (although last year's ''Translations'' was superlative).

If the productions are sometimes dull, it's because the fledgling Huntington is still finding its identity. After two years, it's now starting to gel. Its season - Noel Coward's ''Design for Living,'' Wendy Wasserman's ''Uncommon Women and Others,'' ''Cyrano de Bergerac,'' British playwright David Hare's ''Plenty, '' and ''On the Razzle,'' adapted by Tom Stoppard from a play by Johann Nestroy - started out disappointing, but has picked up steam.

The Huntington's theater lends itself to traditional plays. It's large - 850 seats - with a proscenium stage, lots of warm wood, and good acoustics. Actress Ingrid Sonnichsen, playing in ''On the Razzle,'' says, ''It's a real theater, it's not streamlined, not modern. It even sounds like an old theater.''

The Huntington shines in production values. From the silver, black, and bronze art deco apartment created for ''Design for Living'' to the inn bursting with brass pots and splintery wooden tables in ''Cyrano de Bergerac,'' sets and costumes are a high priority.

Boston Shakespeare Company

You won't find traditional costumes, sets, or interpretations at the Boston Shakespeare Company.

This company is in many ways the young upstart down the street. This year, artistic director Peter Sellars presented a chamber version of ''Midsummer Night's Dream'' done by four pajama-clad actors, a vivid ''Mother Courage,'' a truncated Japanese No ''Macbeth,'' an audacious ''Pericles,'' an evening of Chekhov and Beckett one-acts, and New York's Wooster Group with its mixed-media ''L.S.D.''

Purists may have a hard time with Mr. Sellars. He tends to slash plays rather radically, have characters say one another's lines, and use bizarre lighting (hand-held flashlights). Stodgy, it's not. But if sometimes too precocious, he has fresh insights, style, and wit. And he's a whiz at creating effective sets and costumes on a shoestring budget.

Although the company has been in Boston since 1975, this was its first season with Sellars as artistic director (and possibly its last, since he's taken a position with the Kennedy Center in Washington), and its second in the new 400 -seat space in a former school.

It's not considered by Actors Equity, an actors' union, to be in the same category with the other resident professional companies, since it uses nonunion actors.

With no university connection, finances tend to be precarious; lack of cash flow almost forced the company to close its doors last year. Sellars is hoping to wean the theater away from subscribers, substituting a plan whereby audience members would become shareholders and receive passes to the shows.

''What's so strong in this town and what we'll continue to work with is the musical community and the museums,'' says Sellars. He has presented pieces in conjunction with the Museum of Fine Arts and the Institute for Contemporary Art. This summer he will direct ''Cosi fan tutti,'' in Ipswich, Mass. Sellars sees all this activity as part of an ''ongoing direction of work in which all are related. We want to become part of the landscape.''

Are all three of these young companies likely to become permanent features in Boston's cultural landscape?

''People said there wouldn't be enough audience to support three theaters,'' says Marty Jones, the Huntington's director of marketing and public relations. ''Well, we're proving that there is. We're each such different things that we're not in competition for the audience. It's really a vibrant surge; I think we're turning the town around.''