Rabble-rouser Michael Moore may have cornered the market on commercial documentaries, but Christopher Guest has established an equal rep with mockumentaries.

The writer-director has played crucial roles (behind and in front of the camera) in three of the funniest phony docs ever made. Now his latest piece endeavors to position itself alongside the holy trinity of “This is Spinal Tap,” “Best in Show” and “Waiting for Guffman.”

Guest occasionally succeeds with “A Mighty Wind,” a send-up of the 1960s folk music scene. Yet there’s a lingering sensation of disappointment to the affair, mainly because the movie often resorts to delivering the same old song.

A certain amount of familiarity is to be expected from a film directed and written (along with co-star Eugene Levy) by Guest. It contains virtually the same 15-person troupe of actors from his previous two efforts. The plot is structurally identical: A motley group of performers is brought together to appear at an event/competition that serves as the film’s climax.

There’s also the overlooked (or forgotten) fact that several specific jokes have been recycled. The film’s faux trio The Folksmen originally debuted in a sketch introduced by Guest and Harry Shearer during their 1984-85 tenure on “Saturday Night Live.”

These elements don’t stop the picture from being frequently hilarious. It’s just that a certain amount of freshness has been sacrificed in the process.

In “A Mighty Wind,” the surviving children of pioneering folk promoter Irving Steinbloom decide to throw a memorial concert in honor of the man’s passing. They reunite three of the legendary acts of the day: the insistently chipper New Main Street Singers, the more traditional Folksmen (Guest, Shearer and Michael McKean) and the estranged duo Mitch and Mickey (Levy and Catherine O’Hara).

Folk musicians don’t provide quite so easy a target as Guest’s previous subjects — they’re not as uniformly dim as heavy metal musicians, as naive as small-town Midwesterners or as bonkers as professional pet show owners. Nor are their songs as innately funny. (Don’t expect any comedic epics like “Stonehenge.”) So the filmmaker chooses to extract most of the humor from the pure dysfunctional anxiety that nearly all the performers exude.

Harry Shearer, left, Michael McKean and Christopher Guest star as a reunited folk group in the fake documentary A

It’s here that “A Mighty Wind” lands some memorable shots. The funniest of the bunch are The New Main Street Singers, who are first shown performing at the base of the “Snap Dragon” roller coaster at a Six Flags-type amusement park. Decked in outfits that would be too square for an Up With People audition, the octet is the definition of wholesome. Of course, some members also practice a unique form of witchcraft that draws its vitality from worshiping colors.

The film’s centerpiece involves the reluctant reunification of Mitch and Mickey. After years battling depression, Mitch is now a burned-out shell of his former clean-cut troubadour. And the raven-haired autoharpist Mickey is a housewife who hasn’t performed in decades.

In these roles, Levy and O’Hara give the movie its soul. The bushy Levy joins that elite group of modern comedians (Jack Black and Will Ferrell come to mind) who inspire laughter simply by showing their face. His speech-hampered Mitch provides a good chunk of the film’s best lines, even though some audience members may grow annoyed by his admittedly broad characterization.

Interestingly, the most powerful scenes in “A Mighty Wind” aren’t the result of humorous jabs; they stem from the dormant emotions involved in the reunification of this songwriting duo. This leads to a wordless sequence on stage that is truly heartwrenching.

If only the other characters provided such impact.

So many folkies are introduced with intriguing quirks that it’s a letdown when these gags don’t pay off. For instance, great effort is spent establishing the disdain between the Steinbloom siblings (led by Bob Balaban), although there are no internal repercussions beyond the opening scenes.

Laurie (Jane Lynch), the perky wife and bandmate of Main Street leader Terry (John Michael Higgins), goes intro great detail about her history in the adult film industry, but then this trait is abandoned. Why allude to the fact that she was infamous for an unspecified sexual technique if it somehow can’t be worked into the plot later at a more awkward moment?

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Most frustrating is that the entire relationship between The Folksmen is a crescendo to nothing. Their festering arguments merely cease. The act’s whole inclusion seems to be to set up one visual punchline in the epilogue.

Guest appears caught in a trap where he must find roles for each past participant in his mockumentaries. This results in underdeveloped cameos that fade in and out with little purpose.

“A Mighty Wind” doesn’t blow. But it fails to conjure the type of comedic hurricane that fans of Guest anticipate.

Eugene Levy, left, and Catherine O'Hara star as an estranged songwriting duo who gets back together in A

Rating: 1/2(PG-13)sex-related humor1 hour, 32 minutesLiberty Hall, 642 Mass.