The war at home: "Cyrus"

The Fox Searchlight-backed Cyrus is further proof, after Universal's Greenberg, that mainstream Hollywood executives have discovered mumblecore, and only about three years after that ultra-low-budget movement could be considered cutting-edge. The directors are the Duplass brothers, who gave us one of mumblecore's archetypally trifling texts in The Puffy Chair, but the producers are no less than Ridley and Tony Scott, giving another pair of filmmaking brothers a leg up the career ladder. Narratively, the focus falls on not one but two of life's muttering misfits, but Cyrus betrays its commitment to upnotes and easy redemption in an early scene in which the kind of awkward social gathering that has become a staple of the mumblecore form is transformed into a swinging dance party through the liberal application of the Human League's "Don't You Want Me" - a song that would simply be beyond the means of a struggling off-indie filmmaker.

It's at this party that washed-up, just-divorced fortysomething John (John C. Reilly) meets Molly (Marisa Tomei) while under the influence of Red Bull and vodka, and peeing in the bushes. Molly is nurturing and remarkably tolerant - the ideal woman for a sad-sack such as John, you'd say, except she already has another male in her life: her son Cyrus (Jonah Hill), a 21-year-old stay-at-home and putative musician who does everything and goes everywhere with his dear mama. She, in turn, displays a similar concern for her boy, leaving the door between their adjacent bedrooms open, in order to let out Cyrus's purported night terrors.

The casting gestures in the direction of New American Comedy, leading to expectations of something not dissimilar to the Reilly-starring Step Brothers, with two rival boy-men duelling for a third party's affections. Except that a film in that tradition would have had some brute comic force behind it (no doubt with the side effect of violent slapstick and pratfalls), where the gag-like episodes in Cyrus involve either passive-aggressive scheming or overly intimate revelations intended to make the audience shift in their seats a little.

True, the film is less irksome than Greenberg. The Duplasses strike you as genial souls, and they have an easy way with their performers. (The pairing with the firebrand Scotts is presumably a prime example of creative opposites attracting.) Reilly is all rumpled sincerity, and Hill - heavier here than in other recent appearances; when Cyrus hugs Molly, he's like a human millstone around his mother's neck - is funny in a constipated sort of way, amply demonstrating the comic value of a fat man at a synthesizer. Tomei is her usual appealing self, albeit in a role that seems barely there, what little there is barely making sense. Everyone's dialling it down, though: with its words and ideas falling between any number of stools, it's finally a flimsy, never especially satisfying hybrid, one so low-key it has nothing really to say about relationships. Call it whispercore. Or worse, perhaps: mutecore.

Cyrus opens in selected cinemas from Friday.