Every week this summer, we'll be taking an historical tour of the Hollywood blockbuster by examining an older film that is in some way a spiritual precursor to one of the weekend's wide releases. This week: there are not many living filmmakers whose style and interests would seem to make them a worse fit for making a musical than Clint Eastwood, and yet here he is, counter-intuitively making Jersey Boys. Of course, this is not, notoriously, Eastwood's first encounter with the musical film genre.

My suspicion is that here in the 21st Century, most people who've heard of it are familiar with the 1969 film Paint Your Wagon from a rather nasty parody of it that cropped up in a ninth season episode of The Simpsons, where it's lampooned with generic Wild West music and insipid lyrics like "We ain't braggin' / We're gonna coat that wood". This isn't fair at all - it has given all of those people an unduly optimistic and pleasant impression of what really is one of the very worst studio musicals of the 1960s, the same decade when the studio musical turned into a gaudy monstrosity of bloat, tacky set design, and overall misery (there are good '60s musicals, of course, but they are few in number).

Adapted with an exceptionally loose hand by Paddy Chayefsky from a 1951 stage musical by Alan Jay Lerner and Frederick Loewe, the film tells of a most unlikely friendship during the California gold rush, between grizzled drunken prospector Ben Rumson (Lee Marvin) and the younger man (Clint Eastwood) he shanghais into being his partner without even bothering to stop and learn his name or much of his background. They're among the first to stake claims in a region that eventually sprouts the boom town No Name City, with an all-male population till the fateful day that a Mormon shows up with his two wives. The male population of the city enthusiastically convinces him to auction one of them off, and an immeasurably drunk Ben puts in the winning bid, over Pardner's objection; and so it is that their little homestead blossoms from two men with absolutely clear-cut and unmistakable homoerotic undertones to two men and one woman with what turn out to be polyamorous overtones when Elizabeth (Jean Seberg), Ben's bride, confesses that she loves them both so much, and if a Mormon man can have two wives, why can't a woman have two husbands, anyway? Meanwhile, gold lust still burns in the heart of all the No Name citizens, and Ben's scheme for finding as much of the yellow stuff as possible ends up altering the face of that patch of the wild West beyond hope of returning to the simple, peaceful anarchy where a roaring pioneer like he can be content.

All of that takes place over the course of 158 minutes. And no matter what problems someone might tell you end up torpedoing Paint Your Wagon - the leads' inability to sing, the generally anemic quality of the songs, the stupefying sexual politics, or the general problems in staging a big-scale musical on a location shoot in the Oregon woods - that's what does it. It's the utter, air-sucking indulgence of a zippy little Western comedy that works almost solely because Marvin is impeccable as a surly old man given to sarcastic asides and comic bluster, stretched out to more than two and a half hours, a solid hour more than it can possibly survive. In attempting to lighten Chayefsky's darker, satiric concept for the story (the shape of which can only be guessed through the final product, though certainly satire is just about the only way that the film's attitude towards woman could possibly be converted into something digestible), Alan Jay Lerner - producing and writing the final version of the screenplay - and director Joshua Logan succeeded only in making something frivolous and empty-headed that's far too agonisingly protracted to possibly work as a deft piece of audience-pleasing fluff.

Not that the other problems aren't problems; they're all problems. Paint Your Wagon is a film where problems rain down like angels' tears. The most immediately accessible is its failure as a musical. Onstage, the show only really boasted two real stand-out numbers that could stand with top-tier Lerner and Loewe (it precedes their best work by a few years: My Fair Lady and Camelot in 1956 and 1960, with the film Gigi right in between): "They Call the Wind Maria" and "Wandrin' Star". And this remains true in the movie, but the gap in quality is far more pronounced, with five new songs with lyrics by Lerner and music by AndrΓ© Previn, all of which are perfectly dreadful. When a musical is as dreary to listen to as the film Paint Your Wagon, the time has come to back up and fix it, since music is a pretty key element in the form. Anyway, the songs aren't nearly as big a problem as the singers: "Maria", performed by Harve Presnell, is the only number in the film performed by a trained musical theater artist, while Seberg was overdubbed by Anita Gordon, who at least had some professional singing experience. Eastwood and Marvin, famously, were left to their own devices, with mixed results; most of Ben's numbers are such that a certain gravelly flatness works fine, though it's no loss that Marvin never saw fit to release an album of standards. Eastwood, though... sheeyit, he's bad. The cracking, raspy singing he does at the end of Gran Torino, 39 years later, is legitimately better; at least it has feeling. What the actor is up to here is merely unpleasant, nasal baying that gets across no emotion and is too droning to even be amusingly terrible.

Eastwood is pretty droning in general; he wasn't happy with the shoot and looks it (supposedly, his displeasure with the experience of making Paint Your Wagon was a definitive moment in his decision to start directing). Seberg is even worse, which I imagine has something to do with the impossible character she's playing, an irreconcilable mixture of feminist impulses and deeply sexist baggage, a woman that the film paints as an object and then tries and badly fails to use as the focal point for a satiric indictment of frontier masculinity. Marvin gets away unscathed, I guess, in a burly comic role that requires little but a mean attitude and ability to holler out laugh lines; it's enough to make the film endurable, but certainly enough to make it enjoyable.

It's such stately, overbearing slog: by no means bleak as the worst of the late-'60s megamusicals (the reek of 1967's Doctor Dolittle is hard to ignore); I don't even know that it's as dispiriting as Logan's other Lerner and Loewe adaptation, Camelot (also from '67), which takes better material and leaves it even more waxen and dead-eyed, with nothing but some pretty fucking terrific sets to recommend it. At least Paint Your Wagon, with real trees and real dirt to guide it, feels like a living thing; a suffering thing, that would be better put out of its misery as quickly as possible, but a living thing. Logan, mind you, was a pretty fine director for making bloated movies that needed to be euthanised as quickly as possible: coming to movies from Broadway, he never did quite figure out what to do with the camera or how to coax his actors into giving movie-scale performances that suggested the bombast of the stage without swamping the viewer. His movies tend to feel at once overwhelming and shriveled up, lavish with mean little inhumanity lurking where the actors are meant to be, and even by those standards, Paint Your Wagon is a disaster: even with the usually infallible cinematographer William A. Fraker behind it, the film boasts almost no interesting shots, and all of the ones it stumbles happen in montages or establishing moments, never with the characters. It manages to feel stagebound even outdoors (the scenes on the streets of No Name City are annoyingly flat), and much too close to the actors most of the time. The only time it comes life at all is during the slapstick comedy, and being as it is slapstick comedy from 1969, it's of an especially shrill sort.

Basically, nothing goes right, anywhere in the movie: the best that can be hoped for is things which fail to go wrong. It's a tedious bit of drudgery not buoyed up by its music at all, telling a muddled and at times actively unpleasant story anchored by actors who transparently don't know what to do with their parts. It's not individually the movie that killed of the musical - in fact, it earned a lot of money, it just couldn't turn that into profit owing to a ludicrously costly price tag - but as part of the cluster of films that led to the genre's suffocation in the early '70s, Paint Your Wagon makes it eminently clear why what was at one time the most popular form in all of cinema spent some three decades in exile. Any time a genre reaches this point of autoeroticism, the only thing for it is to take it behind the shed and shoot it.