"This Is Spinal Tap" is a treasure not just among rock spoofs but among rock 'n' roll movies in general. Whenever I see it, I can't help being touched by the moment when Nigel and David talk to an interviewer about how they first met and the song they first wrote together. When they harmonize on a few bars of that little skiffle tune, it brings home -- for real and not just for comic value -- the inexplicable and deep-rooted love for the music itself that generally brings real-life musicians together in the first place.

But with that one exception, "This Is Spinal Tap" is played completely for laughs -- laughs that its devotees strip mine with repeated viewings. How much devotion to Spinal Tap as a phenomenon is too much? On his Spinal Tap fan site, surprisingly levelheaded Tap nut Chip Rowe notes that action figures of Nigel, David and Derek will soon be available at $25 to $30 each. He also, sensibly, questions the sanity of the Spinal Tap fans who, via auctions on eBay, spent $510 for two tickets to the movie's Tuesday premiere in Hollywood and $910 to see the band's private gig at House of Blues afterwards. A quick check on eBay reveals that a copy of the now out-of-print Criterion Collection "This Is Spinal Tap" DVD (the new MGM DVD, with new features, replaces it) recently sold for $96. It may not be "Star Trek," but "This Is Spinal Tap" obviously strikes a pleasurable nerve with the collective rock 'n' roll subconscious.

On one hand, the idea of a new DVD release of "This Is Spinal Tap" seems silly. The old Criterion release, besides a number of deleted scenes, included two running commentaries -- one with Reiner and the other with Shearer, Guest and McKean, and both riotous. On the other, the new commentary included on the MGM DVD (which was unavailable at press time) sounds like a stroke of brilliance: The actors comment on the film scene by scene in character, denouncing DiBergi's work as a hatchet job. It's a way of giving the actors another chance to improvise on their great invention, 16 years after the fact. And because we can hear but not see them, it's as if time hasn't changed them -- a sneaky way of achieving the ultimate rock-star fantasy of never growing old.

The new DVD release also includes the original's selection of deleted scenes, among them a moment that defines in particular Guest's pitch-perfect, off-the-cuff intelligence. Reiner, as DiBergi, asks Nigel what he might hope to be if his rock-star career were to end. Nigel says that he'd like to be a surgeon, to which DiBergi queries, "Do you think you'd be good at it?" Nigel waits one perfect beat and replies, with his typical cocksure cluelessness, "I like surgery."

Of course, you could take "This Is Spinal Tap" apart moment by moment. You could watch it a dozen times and memorize every gag, or pay $500 for a chance to glimpse its stars from afar. But the more you re-embroider "This Is Spinal Tap," the more you run the risk of fossilizing its weird magic. I plan to watch "This Is Spinal Tap" only once every 10 years or so, although perhaps never again in the dentist's chair. And at the risk of going on far too much about a movie that I think of as one sustained note of rock 'n' roll pleasure, I'll stop here. At 10.

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