The brassy, mocking tone that corrupts Robert Altman's new movie," A Wedding," is accentuated by the sound of fanfares. An orchestral fanfare begins the opening sequence of the wedding ceremony itself, a would-be posh affairs at an Episcopal church. When the action shifts to the principal setting, a suburban estate where the reception is scheduled to be held, fanfares kid establishing shots of the facade and the camopied tables in the back arranged by the catering service.

Musically and pictorially, Altman can't hide his condescension. He has invented a wedding party, ostensibly a misalliance between old but tarnished Midwestern aristocracy and new, unsouth Southern wealth, that seems to inspire him to nothing but stale jokes and complacent contempt. He seems to be above it all, like the aged matriarch played by Lillian Gish who expires peacefully in her bed before the reception begins, sparing herself the anxiety and disorder the surviving members of the wedding are compelled to experience.

Altman may have hoped to revive the working method of "Nashville" in a setting designed to foster a classic American comedy of manners worthy of such foreign prototypes as Jean Renoir's Rules of the Game" and Ingmar Bergman's "Smiles of a Summer Night." Unfortunately, it's an unruly, unrevealing attempt at social comedy, a "Sneers of a Summer Night" that quickly degenerators into a protracted game of Get the Guests.

The complement of characters in "Nashville" is supposed to have been doubled in "A Wedding." If one felt like counting, perhaps 48 characters could be identified. The quatitative gain happens to be involved with the drives of frustrations of anyone in particular.

As in "Nashville," the cast was encouraged to improvise scenes and dialogue from preliminary character sketchers. What's missing in "A Wedding" is a controlling creative vision. Altman suggests a coach who's four-deep at every position and can't decide who's going to be first, second-third - and fourth-string. The result is that while everyone gets some game time, no one does much scoring.

There are players who ought to score decisively. For example, pairing off Carol Burnett, cast as the mother of the bride, and Pat McCormick, cast as an uncle of the groom, in an afternoon of sudden, furtive passion could have led to some inspired comic by-play and given the film at least one focus of human interest. It doesn't, though, Burnett and McCormick tried.

Indeed, the direction is so slack and the editing so disruptive that McCormick's declaration of love lacks both a preamable and a suitable setting. When he begins clutching Burnett in full view of the other guests while dancing at the reception, you can't decide why.

The truth is that McCormick's inability to control himself probably reflects Altman's desire to depict the characters as oblivious vulgarians. The wedding ceremony itself is staged with a coy sloppiness that leaves one in instant doubt about the comic authenticity of the proceedings.

Then the guests return from the church, Altmans spends a merry quarter hour or so on redundant jokes about their desperate need to get to the bathroom. A security patrol, captained by John Considine, who pieced together the scenario in collaboration with Altman, habitually accosts members of the family, beginning with Nina Van Pallandt, the mother of the groom. It's as if the filmmakers had decided to invent a preposterous role for the guards to make up for their failure to supply real crashers.

The lack of progress may be epitomized by the two scenes of lustful repartee between Robert Fortier as the gardener and Mary Seibel as (I think) an aunt of the bride. Upon first meeting she says, "My second husband was a gardener. He couldn't mow the lawn." With a knowing smirk he replies, "I know the feeling." When next seen he opens with, "You got some hedges that need trimming?" She answers, "I got a whole lawn that needs trimming."

This low point in the history of double-entendre is all too typical of the film as a whole. When Altman brings the supposedly contrasting families of bride and groom into contact at the reception, the outcome is not high comedy conflict and confusion but a collection of scandalous revelations every bit as stunning as the punchlines.

The groom's mother is a drug addict. One of his aunts has been carrying on an affair for years with a loyal black retainer. The bride's sister is a feebleminded nymphomaniac, impregnated by the groom. The wedding coordinator is a lesbian. The groom's father was a commoner. Simply sensational stuff.

It's impossible to take comfort in the illusion that Altman is working out fascinating stylistic conceits in the absence of fascinating content. On the contrary, his technique seems to come unraveled as a consequence of trying to repeat the format of "Nashville" without emotional commitment or fresh social commentary. If anything, Altman cheapens the format and falls back on wholesale cynicism, his customary last resort when invention or sympathy fail him.

To a great extent those molely family scandals smell from a lack of conviction. They constitute put-up evidence of correction. Altman's inability to capitalize on his own casting brainstorms is especially derelict. The potential comic chemistry between Burnett and McCormick, the humorous affinities between Burnett and Amy Stryker and Mia Farrow in the roles of her daughters, the melancholy beauty of Dina Merrill and Lesley Rogers as deceived wives an opposite sides of the family-all these resources are negligently used. You wonder why he bothered assembling them in the first place.

Eventually, the ineffectual father of the groom emerges as the filmmaker's mouthpiece. Partrayed by Vittorie Gassman, this unassimilated Italian resolves to say Goodbye to All That after years of opportunistic submission to the will of his wealthy benefactors. He confronts the late, uncomplaining matriach with a declaration of independence: "So, Nettie, you can rest now and I'm glad. There is nothing left for me here. I think I am going to take my leave."

Perhaps the wedding party is another wayward metaphor for the segment of spoiled society - vulgar, mercenary show business - Altman feels wedded to but habitually frustrated by in his pursuit of an artistic vocation. It appears that he's trying to reject something symbolically. Perhaps the Hollywood subtext, which also lurked beneath "Nashville," "Buffalo Bill and the Indians" and "The Long Goodbye," has gotten tangled up with memories of a Midwestern upbringing dominated by women or oppressed by snobbery and social climbing.

At any rate, "A Wedding" remains an unrewarding motivational mystery. When Gassman and his brother, played by Luigi Proietti, leave the mansion at the fadeout, the gesture seems more puzzling than impressive. It's as whimsically cavalier as James Caan and Burt Young sailing away at the end of Sam Peckinpah's "The Killer Elite" or Altman pledging $2 million of the probably non-existent profits of "A Wedding" to ERA. Those bombastic fanfares backfire on Altman. He goes out of the way to create ambitious expectations he's either unprepared or unable to satisfy.