Multimedia man Altman plunges into . . . opera?

Hollywood's loss, it seems, is everyone else's gain.

Stung by a series of box-office disappointments, director Robert Altman - of ''M*A*S*H'' and ''Nashville'' fame - stalked out of the movie world recently, determined to try his hand at other media.

Since then, he has staged Broadway and Off Broadway plays, and dabbled in cable television. He has also directed a non-Hollywood film with the unlikely title of ''Come Back to the 5 and Dime, Jimmy Dean, Jimmy Dean'' that has been well received in Europe and has now opened in the United States.

And now, opera. Altman has tackled a major contemporary work: ''The Rake's Progress'' by Stravinsky, a haunting mixture of modernist methods and Mozartian mannerisms, neoclassic nostalgia and Faustian fantasy.

The results here at the Power Center for the Performing Arts were dazzling. Nestled in an academic setting - the show was sponsored by the University of Michigan School of Music - director Altman was free to soar above the ''commercial'' considerations that came to hamper his film career.

It was clearly a liberating opportunity for him, and it may pay dividends back to the movie world, if a film is now made (as has been hinted) from the stage production. Today as ever, there can be little doubt that Altman is among our boldest and most imaginative directors.

This bodes well for his next project, another musical extravaganza due early next year: a $3 million Broadway show, scheduled to open in the spring, based on the work of vintage American composer Louis Moreau Gottschalk.

What led Altman to take on the world of opera? ''I don't know,'' he told me after a stunning performance of ''The Rake's Progress'' the other night. ''It's an idea that's been bouncing around my head for a while,'' he added, smiling at his own vagueness.

Part of his motivation may have been the chance to work on a scale as large as some of his biggest Hollywood projects. ''I've always wanted to get this many people on a stage at the same time,'' he cackled, referring to scenes in which nearly 150 people swarm around the setting at once - scenes that would almost certainly be too costly outside the walls of academe in a conventional opera house or theater.

Then too, Altman's film work has long had a certain musical structure. Some of his best pictures, such as ''3 Women'' and ''A Wedding,'' are based more on developing themes than traditional storytelling techniques. The soundtracks of ''Nashville'' and ''A Perfect Couple'' resound with music almost as much as an out-and-out musical like ''Popeye. And don't forget that Altman is not the first filmmaker to invade the musical stage. Indeed, both Ingmar Bergman and Ken Russell have directed productions of ''The Rake's Progress'' itself.

In any case, Altman's edition of ''The Rake's Progress'' showed a confident approach to the perennial challenge of matching images with sounds. Taking some cues from William Hogarth, who originated the ''Rake's Progress'' in his 18 th-century paintings and engravings, Altman has carried the theme to its logical - and illogical - conclusions.

Physically, the undertaking must rank with the grandest ''grand opera'' in recent memory. The stage creaked under a huge metallic cobweb of platforms and scaffolds. On it were draped scores of bizarrely costumed figures representing both the sublime and (more often) the phantasmagoric aspects of the story, which centers on an ambitious young man who strikes an unwitting deal with the devil.

Inanimate objects took on unexpected life, as when a clock chimed in Stravinsky's score, and suddenly its dial was spectrally embodied by a huge ring of performers. It was part circus, part reverie, part nightmare, part sleight-of-hand, and part sheer fun - all managing to serve the libretto (by W. H. Auden and Chester Kallman) rather than merely distracting attention.

Perhaps the most amazing thing about this production is that it seemed intimate, notwithstanding the hubbub that surrounded it. For all the fury of the staging, the musical personalities of the main figures were never neglected.

Indeed, this would have been a strong and involving show if only the nine singers had been visible, so clearly did they enunciate the English text, and so vigorously did they attend to the acting chores that often seem an afterthought on opera-house stages. Altman the director was not upstaged by Altman the conceptualist. This ''Rake's Progress'' worked as theater as well as spectacle.

The importance of this imposing ''Rake's Progress'' lies not only in its theatrical success, though one hopes it's true that the production will soon reincarnate as a film available to viewers everywhere. What's most encouraging is its evidence that Altman has not given up his yen for excitement and experiment, in the face of his commercial reverses on the Hollywood scene. The new film

More evidence comes from his new independent film. Not long ago, Altman stood as one of the few truly independent voices in Hollywood, a lone explorer willing to put himself and his career regularly on the line for the sake of artistic adventure. His first non-Hollywood picture, ''Jimmy Dean,'' suffers (like his original Broadway edition) from an uneven and sometimes lurid script dealing with the reunion of a Texas fan club. But its one-set visual scheme works even better than it did onstage, shifting moods and tenses with a delicate precision that ideally suits its more intelligent impulses. Apart from its lapses in taste , it shows Altman in full command of his distinctive cinema style - and this at a time when he is moving like a powerhouse through other media, too.