TORONTO - A Spinal Tap reunion means more to Harry Shearer than getting reacquainted with long raven wigs, ridiculous moustaches, zucchinis wrapped in tin foil, leather cuffs or his trusty double bass.

No, as Spinal Tap prepares to release their first album in 17 years, "Back From the Dead," Shearer has had the chance to catch up with his alter ego, bassist Derek Smalls.

So what has the ponderous, pipe-huffing rocker been doing all these years?

"Derek was in therapy for Internet addiction at a small therapy centre in rural England," Shearer said over the telephone from Houston. "He has kicked that, that was very successful therapy."

"He did, in the late '90s, open what was supposed to be the first in a series of hamburger joints in London, called Big Bottom Burgers. I don't think it's gone beyond one and it may have gone beneath one by this point."

Shearer possesses a rapid-fire wit, yes, but he's also grown used to effortlessly jumping back into Smalls' headspace.

Spinal Tap, which also features Christopher Guest as Nigel Tufnel and Michael McKean as David St. Hubbins, is celebrating 25 years since the release of the beloved 1984 heavy-metal satire mockumentary "This is Spinal Tap." They're in the midst of an "Unwigged and Unplugged" tour that finds the comic actors performing as themselves, free of absurd wigs or faux British accents.

Shearer said they got the idea for the tour, which has one remaining Canadian date at Toronto's Massey Hall on May 21, after an impromptu show at the Museum of Modern Art in New York.

The group performs an acoustic setlist with tunes culled from "Spinal Tap" and other Guest-directed movies they've collaborated on, including "A Mighty Wind" (a folk satire in which Guest, McKean and Shearer perform as the Folksmen) and "Waiting for Guffman."

Shearer said the group wanted to do something to honour the 25th anniversary of "Spinal Tap," but felt a smaller tour was the way to go.

"It did not seem like a good idea to do a full-on, big-ass rock and roll show this time around," he said. "This is something we've never done before, we won't be repeating ourselves, it'll be interesting for us and interesting for the fans as well."

And taking the songs out of their original context has given Shearer new insight into the group's songwriting.

"We didn't set out to write bad songs," he said. "We set out to write songs that either in their conception or their lyrical pretension, were funny. It's no fun playing bad music, so we tried to write credible music for each of these acts."

"And so coming at them as ourselves, in certain cases, we're pretty faithful to what you may be familiar with, but in other cases, we asked ourselves how we would approach this song. It's almost like we're covering another act's tune except we wrote it."

"But we have different hats on, if not different heads, and so we have a different musical take on it."

"Back From the Dead," meanwhile, features a mixture of new material, tracks that have been floating around but have never been properly released, and older songs that Tap decided to revisit.

Fans will finally be able to own "Jazz Odyssey" - the "free-form jazz exploration" that Tap was forced to perform after Tufnel quit the group, rendering most of their hits unplayable - and "Short and Sweet," which, of course, Shearer describes as an "endless jam number" with some major-league guests soloing on it.

Other tracks only appeared in the movie in concert versions - "these are the studio versions of the songs, so they sound a lot louder," Shearer notes with a laugh.

The 65-year-old Shearer has been involved with more than one pillar of recent American pop culture. He voices a plethora of characters on "The Simpsons," including Mr. Burns, Waylon Smithers, Ned Flanders and Kent Brockman, and was once a cast member on "Saturday Night Live."

But he still relishes the enduring fascination with "Spinal Tap."

"It's one of the great satisfactions of having done that project, that it's lived this long and still continues to," he said. "I'm always running into people who either are kids or have kids who are discovering it for the first time, and are still really enjoying it and finding it funny."

"I'm always running into musicians of course, not just rock musicians, but country and even classical, who say: 'That's what we watch on the bus."'

"To use a terribly cliche metaphor, I think we struck a chord."

Shearer says he's adjusted to the rhythms of life as a touring musician, but Tap is planning to just do a "one-night-only world tour" at Wembley Arena in early July in support of the new record.

Metal bands tend to have a longer lifecycle than other musical acts - "Almost as if they have no other choices in life," Shearer deadpans.

After 25 years in Spinal Tap - with professional relationships that date back much further - he's still enjoying spending time with McKean and Guest.

Just like the fictional band they created, he says their bond remains unyielding.

"There's a certain chemistry and you know that when you get together, the same things make you laugh and make you happy that always have," he said. "We're older and we're saner now, so that's a plus."

"But the stuff that made us want to come together in the first place is still there."