Robert Altman’s “A Wedding” is done up in the extravagant style of Indian popular moviemaking in the new film by Mira Nair (“Salaam Bombay,” “Mississippi Masala,” “Kama Sutra”). The result is a vibrantly colorful, feel-good ensemble piece, generally genial in tone but with some dark undercurrents. Ultimately it’s too episodic and flighty to stay in the memory for long, but it should keep you gleefully entertained (and occasionally moved) while it’s unspooling.

Set in a New Dehli suburb, “Monsoon Wedding” centers on a hard-driving businessman named Lalit (Naseeruddin Shah) who, along with his more subdued wife Pimmi (Lillete Dubey), is preparing for the arranged wedding of his daughter Aditi (Vasundhara Das) to a Houston engineer, Hemant (Parvin Dabas). The entire extended family is congregating for the nuptials, which are being prepared by Dubey (Vijay Raaz), a slickly ambitious caterer who, in a counterpoint to the central coupling, falls for the family’s shy, lovely maid Alice (Tilotama Shome). Among the relatives on hand are Lalit’s young son Uday (Rahul Vohra), whom his father thinks too soft; beautiful cousin Ayesha (Neha Dubey), who takes up with handsome student Rahul (Randeep Hooda), just returned from school in Australia; another cousin, unmarried Ria (Shefali Shetty); and the family’s wealthiest member, Tej Puri (Rajat Kapoor), a smooth operator with a sinister smile that makes him look like a leering Peter Sellers. Ria and Tej, it eventually becomes clear, share a secret which the former struggles with as she sees Tej exhibiting an ostensibly avuncular interest in an adolescent family member. Eventually her revelations will force Lalit to grapple with how to treat his greatest benefactor while maintaining his own integrity.

Much of “Monsoon Wedding” is of interest from a purely cultural perspective: it’s intriguing to watch as ceremonies and rituals so unlike those to which most Americans are accustomed are carefully arranged. But the point that the picture eventually makes is how strongly Indian traditions have been affected by the west. One can see this not only in the opening shots of local television, in which Aditi works behind the scenes of a garish talk show (with whose marrried producer she’s having an affair–a circumstance which will obviously threaten the wedding), but in persistent grace notes, such as the obsessive interest that Dubey’s mother, whom we glimpse only briefly, has in her stock market portfolio. The characters who fall most clearly in the uncomfortable divide between tradition and westernization are Hermant and Rahul, whose years away from their native land have changed their attitudes without entirely erasing them. They would seem the natural stand-ins for Nair, who studied at Harvard as well as Delhi University; but the linchpin of the narrative is surely Lalit, whose insistence on observing the expected forms will be challenged by the dilemma Ria’s revelations will create for him. How far, the film implicitly asks, can tradition be bent without being lost? Where does the happy medium lie? The picture ends with a traditional ceremony, but one that showcases changed attitudes, too.

“Monsoon Wedding” is aided immeasurably by its brisk pacing, Nair’s dexterity in shifting tone without the result seeming forced, and her estimable cast, whose members skirt the line of overstatement from time to time but never completely cross it. Technically the film maintains a homely feel without looking unprofessional. Ultimately there’s a calculation to some of its plot twists that’s a bit off-putting, but Nair gives it sufficient charm, and Shah the dramatic grounding, to make it an engaging, evocative and intermittently powerful ensemble piece.