NEW YORK, NY.- Ballet makes a great documentary subject, with its rarefied, glamorous world that’s hidden from most viewers. What you see on the stage is just a tiny bit of the whole story. All that beauty and grace is the product of something so arduous that some fiction filmmakers have depicted it as physical and psychological torture (think of “Suspiria” or “Black Swan” or “The Red Shoes”). Even when it’s not that extreme, every ballet is the product of extraordinary commitment and work, and that means there are all kinds of stories to tell.

Those tales provide excellent fodder for nonfiction filmmakers; any ballet documentary is equally about the dance and the dancers. “Swan Song” (in theaters, directed by Chelsea McMullan) takes that to heart. It’s a film with a lot on its mind, one in which you can sense the filmmakers discovering the story as they go along.

“Swan Song” centers on the National Ballet of Canada’s new production of “Swan Lake,” which was mounted in 2022. “Swan Lake,” set to a Pyotr Ilyich Tchaikovsky score, is one of the most widely performed ballets in the world and also one of the most challenging for the central ballerina, who traditionally takes on two roles: the gentle Odette and the seductive Odile.

During her career as an internationally renowned dancer, Karen Kain performed the role many times. After retirement, she joined the senior management of the National Ballet, becoming its artistic director in 2005. When “Swan Song” begins, she is preparing to stage and direct a new production of “Swan Lake” with the company. The work is slated to premiere in 2020, coinciding with Kain’s retirement. It’s her gift to the company and a cap to a 50-year career in ballet.

But of course, nothing went as planned in 2020. That’s the theme of “Swan Song”: Life is unpredictable, and you’ve got to roll with the punches. The film picks back up many months later, after a long period of closure because of COVID and a lost season for the National Ballet, as the dancers return to the rehearsal room and Kain begins her work with choreographer Robert Binet. Taking a vérité approach, McMullan follows not just Kain and Binet but also principal dancer Jurgita Dronina and corps member Shaelynn Estrada.

At times “Swan Song” takes a scattershot approach, but it starts to coalesce around the way that ballet and other artistic disciplines might respond to long-simmering issues related to sexism and racism. It’s no secret to the dancers, most of whom are still in their 20s, that the art form they love has also perpetuated a lot of things they don’t believe in. Kain’s conception of “Swan Lake” wrestles with the ballet’s implicit story about trapped women, a narrative that’s always been there but hasn’t always been foregrounded in productions. Similarly, the company deals with the question of the white tights that all dancers are required to wear and whether they might try to perform with their skin showing instead.

The backbone of “Swan Song” is the journey from rehearsal room to opening night, and if you love ballet, it’s thrilling to watch. But “Swan Song” also gently raises questions about how an old art form might be passed down from one generation to another and what it means for an artist to cap a career while pushing her collaborators into the future. The story here is about more than just the ballet: It’s about the people who are stepping into the spotlight.

This article originally appeared in The New York Times.