“Duets” is a film about karaoke singing, but as the title suggests, it’s also about relationships — how people connect with each other and how they affect each other.

It is bitterly ironic, then, that the “relationship” part of “Duets” is the worst thing about the movie (and there’s a lot of competition in the category of “Worst Thing About This Movie”). Even movies that AREN’T about relationships offer more insight into them than this one does.

We are introduced to six major characters, who wind up in three pairs. Ricky Dean (Huey Lewis — yes, THAT Huey Lewis) is a karaoke hustler, a man who goes from town to town in search of local barroom competitions, pretends to know nothing about it, and then blows the competition away. (Never mind that many of the people he beats actually sing better than he does.) He learns that a former lover has died, and that the daughter who resulted from their affair, Liv (Gwyneth Paltrow), is a grownup now and wants a relationship with her dad.

Next is Todd Woods (Paul Giamatti), a harried and exhausted traveling salesman who gets sick of being on the road and has a meltdown, resulting in a hitchhiking incident in which he meets the quasi-mysterious Reggie (Andre Braugher), who has a gun for reasons he won’t explain.

Finally, and least interesting of the three couples (another category in which there was stiff competition), is going-nowhere-with-his-life cab-driver Billy (Scott Speedman) and trampy would-be pop star Suzi Loomis (Maria Bello). I frankly don’t remember how they meet up, but I know they do, because you see them together for the rest of the movie, each helping the other be more uninteresting.

What these six people have in common, aside from being hollow, worthless characters that you don’t care about, is karaoke. Ricky’s a hustler; his daughter Liv, as it happens, is fond of singing, too; Todd has never heard of it (never even HEARD of karaoke?!), but Reggie soon teaches him; and Suzi sees karaoke as a means to becoming a recording artist.

All of them have entered and won local competitions; the film culminates with the Omaha national championships, where all these people converge in the hopes of winning the $5,000 grand prize. (Only $5,000? People are missing work, flying across the country and staying in hotels, all for a CHANCE of winning $5,000?)

While each of the characters allegedly learns something or becomes a better person in the course of the film, you’ll have to take the movie’s word for it. The dialogue is occasionally snappy, but is mostly cookie-cutter and absurd. (“I’m going out for a cigarette,” Todd tells his wife. “But you don’t smoke!” comes the predictable unfunny reply.) There are also a number of loose ends that are not wrapped up, ideas that are started but left unfinished, and far more karaoke singing than you ever need to see in your life, let alone in one movie.

That karaoke thing is a bugaboo, too. It’s treated very, very seriously here. “Duets” is meant to be a comedy/drama, but we are NOT supposed to be laughing at the inherent absurdity of karaoke or the people who pour their lives into it. We’re supposed to be laughing at other things, like Todd’s inability to find a hotel that will accept his frequent-flyer miles as room payment. It’s what “Waiting for Guffman” would have been if it had ACTUALLY been a serious documentary about small-town community theater: earnestly striving for our respect, but impossible to take seriously.

Bruce Paltrow, father of Gwyneth, directed the film. One assumes Gwyneth appears in it due to not having done her chores at some point in her life, as she is certainly miles above the material she’s given to work with. Huey Lewis, Maria Bello, Scott Speedman — eh, this seems about their level.

D (; R, frequent harsh profanity, one graphic.)