Boston — (The chorus - dressed in Brooks Bros. kimonos and holding attache cases bearing a gold Mikado ''M'' - faces the audience as the curtain opens revealing that all Japan has become Mikado, Unltd.) Chorus: If you want to know who we are, We're the management of Japan. Manufacture every car, Every TV screen and fan. We've all got our MBAs And quaint oriental ways, The setting sun we shall raise, Oh. . . . . . Our system is on the rise, Our secret is in our size: TRANSISTORIZED SAMURAI! Oh. . .
What's going on here? Can this be the mighty Mikado himself, now chairman of the board and leading his employees in televised morning exercises? Is that his son, Nanki-Po, who although ''heir to the chair'' leads the life of a ''wandering wimp''? Is Ko-Ko no longer simply ''Lord High Executioner'' but head of product development for ''a cheap and chippy chopper'' destined to dominate the world market for food processors?
It seems three Bostonians just can't leave a good thing alone. Seeing the possibilities for giving America's chief economic rival a good-natured tweak, they've yanked Gilbert and Sullivan's venerable ''The Mikado,'' one of the most popular theatrical works in the English language, into the 1980s.
''What's New in Titipu?,'' as the trio calls its ''adaptation,'' aims to take a 19th-century operetta that really never had much to do with Japan (it was a satire on British society) and poke a little fun at the ''economic miracle'' under way in the factories and labs of a certain Asian economic superpower.
Not that this is the first time the famous operetta, whose copyright ran out years ago, has been given a twist. In the late 1930s, three versions ran simultaneously on Broadway, including a ''Hot Mikado'' and a ''Swing Mikado.''
But ''no version until now has taken into consideration the changes in Japan since World War II,'' says Tony Hill, a local television journalist who is one of the new collaborators. Although today's corporate Japan of Sony, Toyota, and Hitachi receives a few barbs in the new script (piquing the interest of some Boston high-tech firms, who may back the show), Mr. Hill says, ''We're not trying to preach or moralize. We don't take out the daggers and attempt to disfigure anybody.'' In fact, he says, ''We want to send the first set of tickets to the Japanese consulate.''
The idea for the musical started with Mr. Hill's two partners - Jack Cole, a former Boston TV newsman who now performs a satirical nightclub act entitled ''The Alleged News in Review,'' and John Armstrong, a composer and arranger who has updated the Sullivan score.
They won an early backer in Harry Ellis Dickson, first violinist of the Boston Symphony Orchestra and assistant conductor of the Boston Pops Orchestra. Mr. Dickson has agreed to conduct some performances of the show. Meanwhile, popular PBS morning show host Robert J. Lurtsema is rumored to be lobbying for the role of Poo-Bah.
The three novice impressarios are confident that they will raise the $125,000 needed to bring their production to life at the Charles Playhouse here this spring.
When the show does open, they say, there'll be no reason for loyal fans of Sir William S. Gilbert and Sir Arthur Sullivan to take offense. ''What we're doing is making the show relevant in a way Gilbert had no way of foreseeing,'' says Mr. Cole. ''If those guys were around today,'' adds Mr. Hill, ''I think they'd be doing something like this.''
Gilbert himself, they point out, was known to dabble with his lyrics. Among the people who once appeared - and then disappeared - from Ko-Ko's list of people who ''never would be missed,'' for example, were ''the red-hot Socialist, '' ''the sham philanthropist,'' and ''the lovely Suffragist.'' Those on their modern list include ''the protesting environmentalist,'' ''the ballpark organist ,'' and ''the televangelist.''
But ''Three Little Maids'' singing to a New Wave rock beat? The Mikado making ''the punishment fit the crime'' a la Duke Ellington?
Perhaps it's the very model of a modern major musical.