LOS ANGELES  – It's no joke. The comedic trio behind "Spinal Tap" are hitting the road for a 30-city North American tour next month, and are leaving their heavy-metal guises at home.

Christopher Guest, Michael McKean and Harry Shearer -- accomplished musicians who have been playing together since 1978 -- said on Monday they will perform music from their "Spinal Tap" days as well as from subsequent film collaborations like the folk-music spoof "A Mighty Wind."

They performed a few songs and took questions during a news conference held on the 25th anniversary of the release of the influential mockumentary "This Is Spinal Tap," in which the Americans played deluded English headbangers.

The cult hit spoofed situations that have rung eerily true for real-life bands, such as getting lost while trying to make their way to the stage, being confounded by malevolent stage props, or dealing with problematic drummers.

The film also popularized phrases such as turning the volume "up to 11." And when artists explain away their waning popularity by saying that "their appeal is becoming more selective," it's an inadvertent quote from the movie.

NO ROYALTIES

"It's a cautionary tale that we don't intend anyone to pay heed to," said McKean, who played vocalist David St. Hubbins. "If you're a young guy or gal and you want to be in a rock 'n' roll band, see this movie but do it anyway."

But musicians might want to pay heed to one small factoid: The trio never made a dime from the Rob Reiner-directed movie, their manager Harriet Sternberg told Reuters.

The film, originally funded by TV producer Norman Lear at a cost of $2.5 million, has changed hands at least half a dozen times, and is now owned by French firm StudioCanal. Sternberg said no attempt has been made to recover any royalty income.

The trio's "Unwigged & Unplugged" theater tour begins on April 17 in Vancouver, B.C., and runs through May 31 in Milwaukee.

"We've never gone out as ourselves," said Shearer, who played Derek Smalls, the hirsute bass player famed for stuffing a cucumber down the front of his pants. "It's interesting. After playing characters on stage all these years, we're having meetings now trying to figure out who we are."

They have toured several times before in their Spinal Tap incarnation, but played it straight off stage. Now, "we're gonna destroy hotel rooms," said Guest, the man behind guitarist Nigel Tufnel.

"Actually, at our age, we're gonna hire people to destroy hotel rooms," added Shearer.

The trio have also recorded studio versions of the Spinal Tap songs that appeared in live form on the film and soundtrack. The as-yet-untitled album, bolstered by seven or eight unheard tracks, will be released on May 26.