The comedy revolution referred to by the title of Nick Davis’s sharp and effusive documentary “You Had to Be There: How the Toronto Godspell Ignited the Comedy Revolution…” is the one that took place on television in the ’70s: the creation of “Saturday Night Live” and “SCTV” and everything that grew out of them. “You Had to Be There” makes the case that the Petri dish from which the DNA of those shows was sprung was the 1972 Toronto production of “Godspell,” the Jesus-and-his-followers-as-hippie-clowns musical that had rocked the world when it premiered on Broadway the year before. The Toronto production featured a young Martin Short, Eugene Levy, Andrea Martin, Dave Thomas (all Canadian), and, from across the river, Detroit’s own Gilda Radner — who was the very first performer to be cast on “Saturday Night,” a show created by Lorne Michaels, who was also Canadian.

You might say: Okay, those performers all got their start in “Godspell” — so what? But the niftiness of Davis’s film is that it’s about “Godspell,” and it’s about something bigger than “Godspell” — a pop movement that didn’t have a name yet, a cultural spirit that found its way into existence almost like (laughing) gas gathering in the air. In 1970, before all of this happened, what was comedy? It was stand-up — meaning the old guard (from Shelley Berman to Don Rickles) and also the new guard (the young Richard Pryor and George Carlin and Cheech and Chong). It was the Joyce-on-peyote counterculture antics of the Firesign Theater. It was the scorched-earth satire found within the pages of the National Lampoon. It was early Woody Allen.

But the “Saturday Night”/”SCTV” nexus represented something bold and new: a spark of performance that allowed the next generation of comedy to connect with its audience in an unprecedentedly immediate way. These weren’t just comedians. They were merry pranksters turned rock stars. “Saturday Night,” during the year of its launch (1975-76), came to seem like the Beatles of comedy; “SCTV,” coming from up in Canada, was maybe the Stones. And the root of both shows can be traced back to what was happening onstage, and offstage too, in Toronto during that more than year-long run of “Godspell.” As extraordinary as artists like Pryor and Carlin were, the lifeblood of the new comedy revolution wasn’t stand-up — it was improv. And that’s the spirit celebrated in the documentary, the full title of which is “You Had to Be There: How the Toronto Godspell Ignited the Comedy Revolution, Spread Love & Overalls, and Created a Community That Changed the World (in a Canadian Kind of Way).” What you were seeing in the Toronto “Godspell” were the unofficial first Not Ready For Prime Time Players before they dreamed they’d be on prime time.

“You Had to Be There” opens with the documentary version of a self-deprecating joke — the director’s confession that he’s about to make a film about a fabled theater production…but he has no film footage of it. Because none exists! There’s an audiotape, recorded illegally by Martin Short, who used a cheap cassette recorder and two mics he hung on the chain-link fence that was part of the show’s set. So we do get to hear chunks of the show. And near the end, the film hits us with a special piece of footage that feels like a gift — especially as we see the players’ reactions to it. But why make a movie about a production that was, in essence, never recorded?

It’s like the dilemma Todd Haynes faced when he made his documentary about the Velvet Underground (there is almost no footage of the VU in performance). Davis, like Haynes, comes up with ingenious ways to fill the void. He represents the show with witty animated sequences. The film makes canny use of Short’s cassette tape.

Mostly, though, the players, now in their seventies, sit back and reminisce, so that we get a sense of how Martin Short, for instance, grew up pretending to be Frank Sinatra in his bedroom, and how the prospect of going to college in what was then the very stuffy city of Toronto struck all of them with a faint despair, which is why they landed at the “Godspell” audition, which so many hundreds of people showed up for that it felt (in hindsight) like an “American Idol” cattle call, all of them competing for 10 roles. But various performers rose to the top through sheer moxie, whether it was Radner singing “Zip-a-Dee-Doo-Dah,” Paul Shaffer proving to be such an ace accompanist that he was instantly tapped, by composer Stephen Schwartz, to be the show’s musical director, or Victor Garber, with his soaring voice and beautiful baby face, so nailing the role of Jesus that he owned it from minute one and was, in fact, the only cast member who made it into the 1973 movie version.

Yet that hardly mattered, since what was forming was a community that the players now liken to the artists and writers of Paris in the ’20s. That sounds pretentious, but when we hear another (surreptitious) tape of everyone hanging out in the house where the cast members would gather on Friday nights, after the show (where they’d be joined by folks like Dan Aykroyd, Catherine O’Hara, and John Candy), you hear the effervescence of this group of people all trying to top each other. Comedy was their communication, their jam session, their way of connecting. Life itself had become improv.

“Godspell” is a show with a handful of terrific songs, notably the incandescent Bacharach-esque “Day by Day,” but onstage it was essentially the Book of Matthew staged as a childlike free-for-all. It was “Jesus Christ Superstar” crossed with a vaudeville version of “Pee-wee’s Playhouse.” The actors performing the show eight times at week at the Royal Alexandra Theatre didn’t act so much as they riffed. And by the time Eugene Levy took over the role of Jesus (and refused to wax his body hair off, so they stuck him in a sleeveless T-shirt), it had become a joke that the audience was in on. The actors became local celebrities, and that, of course, was just the beginning. To say that the Toronto “Godspell” ignited the comedy revolution is to embrace a view that feels very chauvinistically Canadian. It’s not anything you can prove. Yet there’s passionate testimony from the likes of Mike Meyers and Lin-Manuel Miranda, who hails the show as “the ’27 Yankees of comedy.” “You Had to Be There” shows you that something was in the air up there, and that it spread like the world’s happiest virus.