“Bohemian Rhapsody” plods, explains, obscures, speculates and flattens. It does not mesmerize. I mean, I wouldn’t miss a train for this. We learn how “We Will Rock You” allegedly sprang from a fit of personal protestation. But it’s news we can’t use. The movie won’t stop telling us things — about the music business and the songs, about Mercury’s tortured sex life. And it fails to show you anything close to what that clip on the subway platforms makes you feel: sweaty.

The musical biography has an impossibly high degree of alchemical difficulty. One performer has to become a totally different performer, and not any performer, just this one star the whole world knows, and it has to be done in a way that makes you believe you’re seeing either the impersonated star or something quintessential about them. Val Kilmer made you believe you were seeing something vitally true about Jim Morrison. Joaquin Phoenix did the same with Johnny Cash. And Jamie Foxx became Ray Charles. Angela Bassett convinced you that if you were seeing if not Tina Turner, then Turner’s indestructibility; and Marion Cotillard, the brittle incandescence of Edith Piaf.

For my money, one of the triumphs of this type of acting is Chadwick Boseman’s James Brown in “Get On Up.” Boseman pumps Brown full of edginess and spite while having to reconstruct Brown as a stage specimen, and part of that reconstruction involves learning to lip sync to Brown. You sense that you’re watching an actor who’s done more than homework. He’s written himself a little dissertation. It’s not an impression of Brown. It’s an interpolation.