The prevalence of documentaries about musicians is a curse, because most of these films do a terrible job of showcasing music. One rare and moving exception is the work of the director Robert Mugge, whose film “Sun Ra: A Joyful Noise”—about the musician and bandleader whose multimedia and pan-cultural activities made him one of the prime artists of Afrofuturism—is one of the most satisfying musical portraits I’ve ever seen. (It is streaming on SnagFilms and Amazon.) The film’s revelatory perspectives on Sun Ra’s work arise not only from the filmmaker’s analytical understanding of it, and the discussions that he films with Sun Ra and other members of the band, but also from his approach to filming music itself, in rehearsal and concert.

To see what’s exceptional about what Mugge does in “A Joyful Noise,” it’s worth considering what more conventional filmmakers tend to do in their films about other musicians. Most often, scenes of performance, whether taken from archival clips or filmed anew for the documentary at hand, run for a few seconds at a time before being covered on the soundtrack by voice-overs. It’s a pet peeve of mine. Even insightful and devoted filmmakers often prioritize conveying information and in the process lose sight—and sound—of the wonder, the miracle, the exertion at the core of the film: the work of the artist whose achievements they’re exploring.

The filming of music is a severe test of directorial artistry, because it’s detached from the moorings of plot and the delivery of dialogue. It’s where filmmakers’ aesthetic character is severely exposed, where they prove whether they can approach the artists they’re filming personally, subjectively, meeting the musicians’ artistic consciousness with their own. It’s often believed, or assumed, that documentary filmmaking is less a matter of style than dramatic filmmaking. Documentaries about the performing arts prove that this isn’t so. What’s more, with documentary filmmaking, aesthetics are also a matter of ethics. The readiness to reduce or subordinate musicians’ art to mere information is more than clumsy; it’s disrespectful. (Working with existing clips of performances is a test, too—film editing and the presentation of archival material is as much a matter of art as is the use of a camera.)

Mugge’s documentary isn’t a biography (for that, I’d highly recommend John F. Szwed’s book “Space Is the Place: The Lives and Times of Sun Ra”); the movie is set intensely and actively in the present tense. He filmed the band, called the Arkestra, in the course of two years, at and around its home base in Philadelphia’s Germantown neighborhood (where Sun Ra and his core of musicians lived and worked together), and in rehearsal and performance in Philadelphia, Baltimore, and Washington, D.C. Mugge doesn’t use archival clips; he films the artists in action, displaying the varied art—of costume, dance, song, and over-all spectacle, along with innovative music—that Sun Ra’s ideas inspire. He also films them talking about their work. The film’s interviews are more like conversations; though Mugge doesn’t put himself into the frame, his rapport with the musicians, and with Sun Ra above all, is crucial to the film’s substance.

Sun Ra, who was in his mid-sixties at the time of the film’s shooting, is first seen amid Egyptian artifacts at the University of Pennsylvania Museum, speaking of the limitations of earthly creation and the creative power that comes from outer space—a prime declaration of the myth-centered futurism that his musical performances dramatize. (To get a sense of the mighty cultural fecundity of the idea, consider its translation into altogether blander realms—the premise of “Star Wars,” which sets its high-tech sci-fi adventures “a long time ago in a galaxy far, far away. . . .”) Mugge films this talk in a single slowly roving, handheld shot that follows the thread of Sun Ra’s thought while also following his amble through the exhibit—paying attention to his gait, to the touch of his hand, and to his facial expressions and his gaze.

In each of the movie’s sequences (approximately twenty, whether brief interludes or extended performances), the sound is recorded along with the image (or close to it). There are no voice-overs, no superimposed graphics or text, only brief title cards between scenes, stating the name of the speaker or the performer or the place where a performance or a discussion is held. The performances are largely continuous and are realized mainly in extended handheld images that rove freely among the members of the band—whether in rehearsal or in concert—and that, above all, coalesce with those performances into compositions that are as distinctive as they are revelatory. They suggest a kind of visual music in themselves. (The concert camera work is by the director of photography, Lawrence McConkey, and David Insley).

The cinematography doesn’t pretend to any artificial smoothness—it darts around, carried from one side of the bandstand to another, dipping to the floor before rising back to the performers, pushing closer, moving back, but maintaining a continuity, like a gaze that may flit about during a performance without losing the thread. Sun Ra blends dance and spectacle with the cosmic fury of his freest inspirations—sweeping an electronic keyboard with his arms, the backs of his hands, with his arms crossed, spinning around, playing while dancing, playing with the tops of his fingers when his back is to the keyboard. One astounding take features the tenor saxophonist John Gilmore, in an exuberant and intricate solo on an up-tempo version of Thelonious Monk’s classic “ ’Round Midnight,” which Sun Ra accompanies on electric organ and then follows with a solo. The camera dips down to the level of the keyboard, showing Sun Ra’s hands along with his face and the band in the background.

In one moving interview, Gilmore—who’d been performing with Sun Ra since 1953 (and led the band after Sun Ra’s death, in 1993)—explains the reason behind his decades-long devotion to Sun Ra: “He was the first one to really introduce me to the higher forms of music.” He’d worked with him for six months—“then I really heard the intervals this one night, and I said, ‘My God, this man is more stretched out than Monk. It’s unbelievable that anybody could write any meaner intervals than Monk or Mingus, but he does.’ ” The wide-ranging performances that Gilmore, one of the key modern saxophonists, delivers in the film, spanning blues-infused post-bebop intricacies and torrential free-jazz outpourings, display in action the liberating power of the musical ideas that he extols.

“A Joyful Noise” showcases some of the advanced music-making that resulted, including the astonishing strumming-and-shredding technique of the alto saxophonist Marshall Allen, who has been leading the band since Gilmore’s death, in 1995, and is still doing so, at the age of ninety-five. It also puts forward some of the advanced political ideas—the alienation, so to speak—that are reflected in Sun Ra’s metaphysical philosophy, notably at an interview done in front of the White House, where Sun Ra wonders about the absence of a “Black House” and sets forth his philosophy of inseparable opposites: “You can’t have a Justice Department that goes out looking for only criminals and never go out looking for people who are doing good. You can’t have justice if you penalize people for doing wrong and don’t do anything to help them when they’re trying to do right.”