For a glorious hour, Straight Outta Compton, which depicts the rise and fall of seminal gangsta rappers N.W.A., seems poised to join the ranks of great musical biopics — suffused with inspiration, instinct and insight into the early days of Eazy-E, Ice Cube and Dr. Dre (and, to less-depicted degrees, MC Ren, DJ Yella and the D.O.C.).

Eazy (Jason Mitchell) stumbling, almost accidentally, onto a unique delivery that set N.W.A. apart from contemporaries while recording “Boyz-n-the-Hood.” Ice Cube (O’Shea Jackson Jr., Cube’s son) relying on his spit-fire journal to catalog thoughts on the entitlement, disrespect and aggression shared by Compton’s troublemakers and peacekeepers. Dre (Corey Hawkins) letting demonic sadness and self-doubt occasionally arise in a man who was often compelled, amid the comparative chaos around him, to remain as unceasingly steady as his legendary beats.

The showman supreme, the social conscience and the sonic wizard are all fascinating on their own, and the actors playing them are uniformly excellent. Like Kevin Hart cut with Terrence Howard, Mitchell blends withering insults with tremulous intensity and mounting insecurity. Along with cutting a similar figure, Howard lends Dre a weariness that comes with shouldering others’ burdens. To watch Jackson … well, only the calendar will tell you that you aren’t actually in 1986. And yet Jackson understands the difference between imitation and essence; Jackson becomes his dad by letting you see the soul behind a face that can sneer and smile with equal charm.

However, the fierce flashpoint that unites the group arrives in a needlessly escalating encounter with cops that spurs Cube to release pent-up anger in the profane polemic “Fuck tha Police.” This electrifying scene is one for the ages, and it reverberates with low, ragged rumbles into today’s racial-tension headlines. Cinematographer Matthew Libatique’s close-ups hit like a battering ram, lingering on frustration, uncertainty and anger until the bubble bursts. Then, with a tsunami of sound, the song kicks in as both a moment of levity (you know what Cube is scribbling on that paper before he slaps it on a table) and a mammoth lament. Outside the booth, Cube claps with skin-flaying force as his colleagues, rapping the second and third verses, capture not just a convincing cadence but years of catalyzing rage.

It’s the unquestionable apex of a film directed by F. Gary Gray — a filmmaker who, whether in music videos or movies, has chronicled members of this crew so long that his authoritative direction feels effortless. Perhaps that easygoing relationship is part of the movie’s third-act stumbles.

Peripheral players like Snoop Dogg and Tupac Shakur pop up for no reason other than to crank another gangsta-rap greatest hit. Biopic syndrome sets in as members fall prey to what N.W.A.’s manager Jerry Heller (Paul Giamatti) calls ego, excess and expectation. Moreover, it dances around tougher questions those outside the legends’ carefully cultivated circles might have lobbed about N.W.A.’s more cheerfully misogynist material or their own well-publicized bad behavior. Produced by Cube, Dre and Eazy-E’s widow, it can feel like winner-sourced history. I’d have preferred more time on personal peccadilloes and less on twisting Suge Knight — a strong-arm mogul who lured Dre away and whose evil needs no embellishment — into a Bond villain commanding his German Shepherd … in German!

When trading impact for incident, Compton is little more than a multimillion-dollar reenactment — albeit persuasively acted and vividly rendered. At 147 minutes, it’s also too baggy. The lengths to which Jonathan Herman and Andrea Berloff’s script offers diverging accounts of certain events (e.g., the dissolution of Dre’s contract) are great. The results are not.

The movie is better when it’s honest about the things upon which Dre, Eazy, Cube and the crew readily agreed. Without being reductive, Compton acknowledges the powerful motivations of money and media exposure alongside the means to express themselves; “they bought the motherfuckers,” Eazy shrugs as the tour bus drives by a demonstrative demolition of their albums, in a bit that’s as accepting of the protesters’ right to speak their minds freely as it is a got-your-money punchline.

Each member is also keenly aware of the morbid fascination their words must have held for pasty white kids in the smallest specks of flyover country — kids like me and my friends huddled in hushed reverence around a cassette player that contained audible contraband, who figured something so taboo and terrifying could only speak truth about inner-city violence, oppression and confusion. There’s also a comparably lighter side to the will-to-power in their words; in a scene when Cube ambushes Eazy and Dre in a solo dis track, they pay begrudging respect to the confidence with which he wields the brand that burns them. (Aside from this and brief, crowd-pleasing comeuppances against journalists or rivals, Cube all but melts away in the second half as he goes solo.)

Compton rallies for a strong finish, hoisted by Mitchell and Giamatti in a blisteringly honest late scene that cuts to the core of the men’s many mindsets and shrewdly plumbs the depths of Heller’s dynamic with N.W.A.: He loved them. He hated them, too. The feeling was mutual. And it was messy, complex and prone to unpredictable and unforgettable spikes in volume and intensity, much like the best parts of Straight Outta Compton. The movie doesn’t feel phony, but it beats an unexpected retreat to safety — a solace far, far beyond the gaze of the greatness Compton gives you at the outset.