Christopher Guest, Michael McKean and Harry Shearer, the merry pranksters and exquisite satirists behind 1984's classic "This Is Spinal Tap," have traded heavy metal for that eerie early '60s interlude when folk music swept America -- when we blew in the wind with Bob Dylan or left on a jet plane with Peter, Paul and Mary.

Written (with Eugene Levy) and directed by Guest, who showed us the addled innocence of community theater in "Waiting for Guffman" and the soiled underbelly of the dog-show circuit in "Best in Show," "A Mighty Wind" posits a 40-years-later tribute in honor of the recently deceased Irving Steinbloom, a folk music impresario back in the day. "Ode to Irving," as it's been named by his perennially worried son (Bob Balaban), reunites the New Main Street Singers, who are still making albums; the Folksmen, a group who had more integrity but fewer hits than the original Main Street Singers; and Mitch & Mickey, a duo who specialized in twee love ballads with lots of "dreams" and "fairy tales" in the lyrics.

The Folksmen are Spinal Tap (Guest, Shearer, Mc-Kean), reincarnated as guys who once wore dickeys and still have that amiable do-gooding disposition so many folkies had. Their songs tend to go like this: "There's a puppy in the parlor and a skillet on the stove!" or, more seriously, "My momma was the cold north wind/ my daddy was the sun" (think, strumming guitars).

The New Main Street Singers, led by John Michael Higgins, Parker Posey and Jane Lynch, are big in Branson, Mo., where their upbeat, homogenized sound goes over big with the upbeat, homogenized audiences.

Finally, there's the entity known as Mitch & Mickey. The still-lovely Mickey (Catherine O'Hara) is now married to a guy in the bladder management biz, but has always worshipped Mitch, her mentor and muse. Mitch (Levy) is the shattered soul (and voice) of the folk movement. He's part Brian Wilson, part Bob Dylan, and whether he'll make it through "Ode to Irving" is about as close to a plot as this movie gets.

Many of these people have been in Guest's earlier movies and they are a tremendously gifted and madcap ensemble. Higgins, Posey and Lynch dress in Teletubby colors and have that crazed happy-face gleam you used to see in Moonies. Shearer's shaved pate and hipster beard make him look like a pixilated Amish farmer, while Guest has lost his middle hair and what's left bushes out on both sides, suggesting a mix of Art Garfunkel, Ron Howard and Ronald McDonald. And watching Levy and O'Hara, who've been working together since the late, great "SCTV" series in the '70s, is like watching Venus and Serena Williams at Wimbledon; their give-and-take is that powerful, intuitive, on-target and inspired.

As was true of "Best in Show," some of the improvised connective tissue isn't as insanely hilarious as the specific parodies. But they help jolly along those who may not get some of the more pointed satire.

However, this isn't a case of you-had-to-be-there, any more than you had to be a metalhead to get "Spinal Tap." So you don't have to be an aging baby-boomer folkie-manque to laugh yourself silly at "A Mighty Wind." But being one may help you catch the tender heart beneath the mockery.