There's a true story about Philip Glass that his chroniclers love to tell. Shortly after his opera ''Einstein on the Beach'' was presented in the Metropolitan Opera House, he was back at his workaday job, driving a Manhattan taxicab. In a posh neighborhood he picked up a chic-looking passenger, who noticed his license on display near the meter.
''Young man,'' she asked in a friendly voice, ''did you know you have the same name as a very famous composer?''
Eight years later, Glass no longer drives a cab or fixes plumbing to subsidize his musical career. Just the opposite. He's a star of the creative world, spinning off a remarkable number of projects - all marked by the pulsing, repetitive style that has become his trademark.
It's still a controversial style, but the composer doesn't mind. ''Polarization is better than bland reviews or none,'' he says. ''And bad reviews rally your supporters!''
Here are a few of Glass's latest enterprises:
* ''Einstein on the Beach'' is due for a full-scale revival this month, again designed and directed by Robert Wilson, with the Philip Glass Ensemble in the orchestra pit. After a Dec. 11 bow at the Brooklyn Academy of Music (BAM), in the vaunted ''Next Wave'' series, it will tour the United States under BAM auspices. Its brilliant recorded version has also been reissued by CBS Masterworks (M4 38875).
* His opera ''Akhnaten'' just finished a run at the New York City Opera, where it sold out weeks in advance. The production, which premiered at the Houston Grand Opera, will travel next June to the English National Opera in London.
* ''Satyagraha,'' another of his ''portrait opera'' series, will be released by CBS next year in a recording with City Opera musicians and will enter that company's repertoire in 1986.
* Glass recently finished the score for ''Mishima,'' a film by Paul Schrader about the life of Japanese author Yukio Mishima.
Other irons in the fire include an opera based on a Doris Lessing novel; a score for choreographer David Gordon; a children's opera called ''The Juniper Tree''; and music for Samuel Beckett's tragicomic ''Endgame,'' slated for the American Repertory Theatre in Cambridge, Mass.
And that list doesn't include another planned collaboration with Wilson, sundry European productions of his operas, or his music for the lighting of the Olympic torch last summer. Or his many nonopera records. Or his busy performing schedule.
With so many projects under way, Glass has been accused of falling back on easy formulas and self-imitation. He admits that's a danger. When asked to write music for a Mabou Mines theater production, for example, he decided to reach especially far toward originality, using an unheard-of combination of double bass and timpani. ''And even then I found myself slipping into familiar territory!'' he says with surprise.
Still, he feels he can dodge the ''sameness'' trap by pushing himself steadily into new areas. And he doesn't think it's wrong to be profilic. He notes that past composers often had prodigious outputs by current standards. And he claims he works hard to produce his many pieces - getting up at 6 every morning and composing until 12 or 1 each afternoon for months on end.
Also, he puts his main energy into his large-scale works, which he calls ''the watershed pieces where I make the inventions I need.'' He dashes off the smaller pieces in between. ''It's relaxing,'' he says.
My latest meeting with Glass took place at his newly bought town house in the East Village section of Manhattan, an unfashionable neighborhood that pleases him with its gritty atmosphere and ragtag street life. ''Akhnaten'' had just bowed at the New York State Theatre, and some negative response had already appeared in the press, but he took it in stride.
Some critics ''think they know what's supposed to happen in an opera,'' he said. ''When it doesn't happen that way, their feelings are hurt.'' Glass is convinced he will outlive his detractors and even claims to feel sorry for them. ''What's worse than being present while a revolution is happening, and not know it?'' he asks with a wry smile.
He feels part of that revolution is the popularity of his work despite hesitation by many critics. ''I've always done an end run,'' he says. ''When I started my own ensemble in 1968, the intention was not to be a victim of the new-music forums and seminars and concerts and publications. You were supposed to pass through that bottleneck, but I simply ignored it. They didn't like what I did, and if I waited for them, I'd still be waiting.''
He also resented the idea of ''asking permission to exist'' from an establishment that seemed ''arrogant and condescending to younger people.'' So as a ''strategy for survival'' he sought a fringe audience on his own. ''There have always been mavericks in American music,'' he says, citing well-known composers from Ives and Ruggles to Harry Partch and John Cage. ''They've always been treated as kind of crackpot figures who existed on the periphery. But now the mavericks are coming toward the center. And that's unnerving to some people. . . . ''
Despite the assertiveness of such remarks, Glass knows he still has growing to do as a composer. He even has a theory about it.
''You start with a language,'' he says. ''And you develop that, perhaps, into a style. That's the stage I'm in right now.''
But there's another stage he hasn't reached yet - where the style becomes a personality. ''That's when you can hear just two bars and know it's Tchaikovsky, '' Glass says. ''It's an instantly recognizable voice. If you look at Mozart or Bach, you'll see they do things that become almost like rules, but they aren't actually in the harmony books. There's something that goes beyond the rules, and becomes almost a personal habit of the artist.''
That's the realm Glass hopes to enter one day. ''This is when music is really interesting,'' he says. ''If you have enough confidence in your musical language , style, and personality, you can do pretty near anything and it'll still be you. But that doesn't come until you're a fairly mature person.'' For now he's content to work toward that maturity - meanwhile hoping the search for a recognizable ''personality'' won't lead to a ''style'' that's too predictable. ''Is it possible for me to write a piece no one would recognize?'' he wonders. ''That would be a trick!''
Glass's leapfrogging from one project to another reflects a wish to pull this ''trick'' off. ''I want the freedom to write in new ways,'' he says, ''on a high level of invention. But all the forces are the other way, whether it's your record company or the people closest to you. The energy goes toward conservation of style. There was a time when I was introducing a different kind of harmony into my music, and people would continually correct the score!''
To fight this, he tries to change the conditions of each new piece. ''The strategy is to find new solutions by creating new problems,'' he explains, ''to goad myself into finding new ways of working. This must be continuously and consciously done. The biggest problem is the inertia of a successful idea. To be truly free is to decide what you want to do, and the hardest obstacles are your own habits, fears, and ability to imagine what the next thing might be. It's the music I haven't written yet that interests me most. I have no loyalties. . . .''
This attitude, of course, could lead to an opposite trap - of straining for variety at any cost. Glass doesn't see this as a major problem, though. ''I've not changed nearly as much as I would have liked to,'' he says. ''And actually, the idea of continuity is interesting. It's a balancing act. In the end you're stuck with your personality. I may favor certain techniques because I just like 'em. The conflict of growth and continuity is a classic conflict that you find in all areas of life. . . . ''
Just now, Glass is determined to avoid the ''typecasting'' he fell into by doing three ''portrait operas'' based on historical people. His next opera will be sung in English and have a conventional story. But he's proud of his trilogy on Einstein, Gandhi, and Akhnaten. ''They're big statements about social issues, '' he says. ''One is on politics, one on science, one on religion. I think I accomplished the idea of treating socialissues as the centerpiece of major works , and that pleases me more than anything else.''
He's also pleased that the Stuttgart Opera in West Germany will mount all three in repertory about four years from now. ''These are theater works,'' he notes, ''and the test of them is only in the theater with a couple of thousand people there.''
Here the composer touches on an unusual facet of his career: his tendency to choose opera, dance, and film as settings for most of his projects. One reason is that he enjoys collaborating with directors, choreographers, and designers. ''It's fun to interface my whole way of working and thinking with other people, '' he says. ''And I like finding new people to work with - it gives me new stimulus and ideas.''
The risks are high, he admits. ''You may not always like what you come up with,'' he says, ''and there's almost no production I've worked on that I like completely. But part of being a good collaborator is allowing other people to do their part of the work. You have to give them a lot of trust, and then hope for the best. And sometimes you come up with terrific things you never would have found on your own.''
Coming up next on the Glass agenda is a smaller-scale enterprise, though - a song cycle with lyrics by Paul Simon, David Byrne, and Laurie Anderson. ''I realized I'd never sat down and written songs just for the sake of doing it,'' the composer says, ''and that was a good enough reason to do it.
''I asked myself, If I were to write songs, what would they sound like? And I didn't know! The answer will be the piece. . . .''