Starring Adrien Brody, Jeffrey Wright, and Beyoncé Knowles. Rated 14A. Opens Friday, February 13, at the Ridge Theatre

Fortunately for lovers of blues and Americana in general, actor-turned-filmmaker Darnell Martin has enough passion for her subject to infuse at least the first half of Cadillac Records with more realism than biopic clichés, and more music than empty chatter.

The writer-director initially focuses less on the artists of Chicago’s Chess Records than on its guiding spirit, tough huckster and occasional Cadillac giver Leonard Chess, played somewhat routinely by Adrien Brody. But the story’s heart is Muddy Waters, brought to life in a career-topping performance by Basquiat’s Jeffrey Wright. A potent catalyst for the nascent electric-blues scene, the ex–Mississippi sharecropper attracted equally compelling acolytes, such as volcanic harp player Little Walter (Columbus Short), and enigmatic rivals, like Howlin’ Wolf (scene-stealing Brit Eamonn Walker).

Also on hand are house guru Willie Dixon (Cedric the Entertainer), the big double bass of a man who wrote many of the label’s biggest hits, and Chuck Berry (a note-perfect Mos Def), who crossed over to the white kids. Some names had to be left out, but Leonard’s brother Phil (albeit a silent partner) is never even mentioned. And how can you convey the scene’s variety without the eccentric presence of Chess star Bo Diddley? His staggered guitar rhythms inspired generations of British bluesmen, but here’s where the movie gets confusing. Some Rolling Stones are spied in a 1963 sortie to Chess Studios (they first came to the U.S. in 1964), followed by Waters proclaiming Elvis Presley “the next king” while watching mid-’50s TV footage. Later, Berry threatens to sue the Beach Boys for ripping off “Sweet Little Sixteen” for their 1963 hit “Surfin’ USA” just before his being sent to jail—in 1959.

More troublesome is Leonard’s vaguely delineated relationship with heroin-addicted singer Etta James. Beyoncé Knowles is surprisingly authoritative in this difficult role, but there is too much of her, and to poor dramatic effect. The music, mostly performed by the cast, remains stellar throughout, but just because these people had the blues, did it serve us right to suffer too?