"Melinda and Melinda" is the kind of experimental movie they'd only let a guy with the clout of Woody Allen make. It begins with a dinner party argument between stage veterans Wallace Shawn and Gene Saks, intellectual gabbers discussing the opposing merits of tragedy and comedy and which genre better serves human needs. Another dinner companion offers a basic story, a test, to see who is right.

The device offers two versions of Melinda (Radha Mitchell), on the run from a troubled past, who shows up out of nowhere at two different Manhattan dinner parties. In both comedy and tragedy, she's recently divorced. Early on, Allen offers subtle hints as to which version he prefers. In the tragedy, her powerful husband has removed her from their kids; in the comedy, she's taken 26 sleeping pills and asks for some vodka to calm her nerves. In the tragedy, she's introduced by friends to a bespectacled dentist named Greg, who must be colorblind judging from the way he dresses; in the comedy, she's introduced to a handsome dentist named Greg who drives a Bentley convertible and answers her observation on the pretty countryside with "Yeah, it's so sexy."

It's obvious which version Ferrell's Hobie is in. Woody Allen comedies without Allen almost always have a stand-in for the aging comedian, and it's the better decision to go that way. "Small Time Crooks," "The Curse of the Jade Scorpion," "Hollywood Ending" and "Anything Else" were not middling movies just because Allen starred in them, but his kooky antics have dulled on screen with age. It's a relief to see him take a backseat for Ferrell, who is commanding in the role, eagerly lapping up his scenes like a dog let in the house for the first time.

Recently Ferrell has seemed to be a ship without a captain, wasting time in broad, overblown roles. There's no better contrast in a comedy career than his last movie, "Anchorman," and his interview with Barbara Walters, the first humorless and the latter absolutely brilliant (at the expense of Walters). In "Melinda and Melinda," Allen and Ferrell come together to make Hobie a bigger, lumpier version of Alvie Singer, and the result should be trademarked and mass-produced immediately. In hindsight, it was a surefire formula: the one needed a body and the other needed a soul. Allen uses the opportunity to sing.

In an early scene Hobie wants to discuss sex, or the lack thereof, with his wife: "Of course we communicate," Peet's Susan yells, "but could we not talk about it right now?"

Susan in turn works on a movie set, where Allen quickly shows his contempt for his own field: "Tell the actors we're doing scene 10 instead of 26," the director hollers at her, with the actors standing right there.

If there's a problem with "Melinda and Melinda," it's a little one-sided. Allen is certainly capable of tragedy, since his comedies always contain elements of the tragic, and vice versa. Just take a look at his brilliant love ballad, "Sweet and Lowdown," which devotedly captures the melancholy lilt of Django Reinhardt's music in moving pictures. Chlo‰ Sevigny and the rest of the supporting cast in the tragedy are engaging, and the story is smart and surprisingly moving. But with the sea parted as it is here, the tragedy is inert by comparison to its better half.

Surprisingly, all this does little to spoil our enjoyment. That the ideas seem at times recycled and the point occasionally obscure hardly seems to matter. This is one of the good Woody Allen movies, full of charming music, romance and comedy. You'll walk out of the theater lifted in spirit, perhaps thinking, I needed that. (PG-13) **** S