I forget sometimes that Rob Reiner used to be a downright excellent filmmaker.

We are now 30 years removed from the release of Rob Reiner’s classic mockumentary This is Spinal Tap. It was the directorial debut film from Reiner, whose next six films would range between the good and the very very good (Sure Thing, Stand By Me, Princess Bride, When Harry Met Sally…, Misery, A Few Good Men). Then he made the garbage burger that is North, and things never really recovered. But that was a damn good 8 years.

In the off-chance you haven’t seen the film, This is Spinal Tap is the mock-rock doc directed by Marti DiBerger (Rob Reiner), who follows band mates Nigel Tufnel (Christopher Guest), David St. Hubbins (Michael McKean), childhood friends who created Spinal Tap, and their current drummer Derek Smalls (Harry Shearer) as they tour the US in promotion of their new album “Smell the Glove”.

I didn’t see This is Spinal Tap when it came out. As I was only a toddler then I probably wouldn’t have enjoyed it if I had. But like most movie fans, I saw it, loved it, and have watched it over and over for years. A few weeks from now will mark the 30th anniversary of the release of This is Spinal Tap, and it’s a great chance to say, once more: I still cannot believe how funny a movie is This is Spinal Tap.

It is so, so funny. So quotable, so eminently weird and enjoyable and filled with joie de vivre that to see This is Spinal Tap is to love it, and to love it is to LOVE it.

Beyond just saying it is funny, though, it isn’t easy to summarize the spirit of Spinal Tap. Perhaps that’s why the film, when it was originally released, garnered only mixed reviews and didn’t perform well at the box office. It is without doubt an odd experience, holding fast to the satiric worldview it creates in the camera within the camera. And that lens allows no separation for audiences. You just have to live with this director as he lives with this very weird band. Spinal Tap is the kind of film that reveals its joys in time. Today it is almost universally heralded, by some considered one of the best comedies ever made.

It is 30 years later and here is why I think This Is Spinal Tap remains a comic masterpiece: because it is so fucking sad. Everything these guys do is inappropriate, almost beyond belief. They are walking talking sexism machines, totally clueless and, amazingly, likable.

Having no idea that they are at best a joke (Lick my Love Pump), and at worst, living a nightmare (Stonehenge), Spinal Tap by sheer will continue to perform, continue to believe in the magic of their artistic vision. No number of mysterious drummer deaths is going to change their belief in their own music. And by holding so tightly to their own stupidity, remarkably, they manage to overcome the nightmare and are just sad enough to be sympathetic, and sincere enough to be likable. Despite being completely unaware of every single thing that takes place around them, Spinal Tap is able to believe, truly and without a moment of doubt, they are the height of rock stardom.

Perhaps the most famous joke in This is Spinal Tap is the result of a manufacturing error on a guitar amplifier. Where other amps only have 10 volume settings, Nigel’s goes to 11. Which, obviously to Nigel, is “one louder” than those other amps. “What we do, if we need that extra push over the cliff, you know what we do? You put it up to 11.“ A meaningless statement made with such conviction and faith in its self-evidence that you can only marvel at what is, frankly, idiocy. When asked why not just make 10 the loudest, equal to 11, Nigel is stumped into silence.

Which is how this movie works, and why, I believe, it remains as powerful as it does. That extra beat, after the initial joke, for the sadness to settle in turns what would be a funny joke (this band is stupid) into a great one (this band is stupid, and that’s really sad). This sadness is funny, but also surprisingly complicated, robust, and not in search of pity. All from that extra beat.

This is the same beat that will take life in the Christopher Guest mockumentaries to follow, and is epitomized in the local theater heart-breaker Waiting for Guffman. These guys are sad. And for some reason, that’s hilarious.

There’s a joke, in the middle of the film that has always summed up This is Spinal Tap in my mind. Their new album “Smell the Glove” has a cover photo of a”greased naked woman on all fours”, with a dog collar around her neck, and a leash held by a man’s gloved hand, pushing the glove in her face. When they’re told their album is being boycotted, and that the cover is too sexist and offensive for the label to release it, David St. Hubbins replies: “If we were serious, if she was actually being made to smell the glove, you’d have a point. But it’s all a joke, we’re making fun of that sort of thing.”

Obviously this is not true. And in defense of pure misogynistic outrageousness, Nigel cannot refrain from chiming in: “It is and it isn’t,” he says. “She should be made to smell it.” To which St. Hubbinns says: “But not over and over, of course.”

Reading this back, here, the joke doesn’t come across. It just sounds gross, and offensive. But this, again, is why This is Spinal Tap works. Suffice it to say, this moment is so funny, and so sad, and somehow, these idiots are still so likable, that This is Spinal Tap, 30 years later, deserves all the admiration you can muster.