The Kennedy Center has joined forces with six other nonprofit arts complexes to speed the flow of musicals -- especially new ones -- to Los Angeles, San Francisco, Seattle, St. Louis, Denver and Washington.

The new partnership, called the American Musical Theater Group, is a response to rising production costs that have made it harder and harder for a touring show to turn a profit with stops in only a few cities. The venture will be headed by Cy Feuer and Ernest H. Martin, who produced the Broadway hits "Guys and Dolls" and "How to Succeed" and now manage the California Civic Light Opera Association.

"We plan to do four productions a year in which everyone will chip in some money," said Kennedy Center chairman Roger L. Stevens, a driving force behind the new venture. Stevens said that the Kennedy Center will participate in three Musical Theater Group shows this season, including a revival of "Kiss Me, Kate" (starring Judy Kaye and baritone John Riordan) and two new musicals still to be announced.

Stevens, Feuer, Martin and James Ryan of Seattle's Fifth Avenue Theatre Management Co. met in Washington a week ago to map out the new venture, and Stevens was in New York last week for another planning session.

The Civic Light Opera sponsors its own 15-week, two-city touring season (in San Francisco and Los Angeles), which will be the nucleus of the Musical Theater Group's intinerary. Last season, the Civic Light Opera offered "On a Clear Day You Can See Forever," "Guys and Dolls" and "The Umbrellas of Cherbourg." And, said Martin, "we didn't earn back our production costs on any of the three. And I don't think it would have been possible.They just cost too much.

"So it became increasingly obvious to all of us that if we could get together and put together at least a 26-week schedule, we'd have a better chance to do the kind of quality shows we want to do."

The Kennedy Center has been having its own musical-comedy problems. Only two brand-new shows -- "Swing" and "Carmelina" -- have played there in the last two years. And the Warner and National theaters have been providing increased competition for the finite supply of revivals and post-Broadway touring productions.

Two of the biggest current revivals --"My Fair Lady" and "Camelot" -- have been forced to skip Washington outright, because, to cover the salaries of stars Rex Harrison and Richard Burton (roughly $50,000 a week each), they needed larger arenas than any this city possesses.

Stevens was offered "My Fair Lady" for the Opera House, but says he refused to buy the $35 top ticket price proposed by the producers. The Kennedy Center currently charges a top of $25 for a musical, and Stevens has tried to keep prices below corresponding levels in New York.

He is also critical of the latest contract agreement between Actors Equity and the League of New York Theaters, which brings the cost of a chorus member (salaries and fringe benefits combined) to about $1,000 a week. Ironically, the rise in such basic production costs has spurred the trend toward star-studded revivals as a way of guaranteeing a big audience. But in the new touring-show economy, "big" means 3,000 to 4,000 seats compared to the 2,300-seat Opera House. So only the largest opera halls and municipal auditoriums can afford to book some of these shows.

The inability of "Sugar Babies" to duplicate its Broadway success on the road is the latest writing on the wall. Despite a cast headed by Carol Channing and weekly income in the $200,000 range, "Sugar Babies" closed in Boston three weeks ago and aborted its planned national tour. The industry word was that the show had simply cost too much and needed to earn nearly $250,000 a week to break even.

The "Sugar Babies" fiasco is a particular problem for the Opera House, which has been left with a gap in its schedule come next June -- a gap that could be filled by "Kiss Me, Kate" or another Musical Theater Group show. One of the new group's projects -- a post-Broadway edition of "Brigadoon" -- will skip Washington, having already played at the National.

As for new works, Martin is optimistic that the Musical Theater Group will be in a strong competitive position to deal with major writers, composers and producers. "Roger Stevens has been the producer of many, many shows," said Martin, "so between us we represent a certain amount of -- that vulgar word -- clout in the industry. So I think we should be able to do more new shows than any of us could do alone."

Martin said he is confident that the Justice Department won't object to the alliance on antitrust grounds -- despite a history of close government scrutiny of the interrelationships between theater management and production. "We don't really dominate a market anywhere," he said.

Coincidentally, one of the participating facilities -- Seattle's Fifth Avenue Theatre -- is located in a building managed by Stevens' real-estate interests. But he has no involvement in running the theater itself, he says.