In “Cadillac Records,” writer/director Darnell Martin simply tries to do too much. The film tells a lot of stories, all of which are immediately related, but several of which deserve their own feature-length films. As a result, none of them is told in sufficient depth for “Cadillac Records” to be a satisfying picture of the emerging black music scene of mid-20th century Chicago.

The film is, I suppose, mostly about Leonard Chess (Adrien Brody), founder of Chess Records, a pioneering record label that mostly specialized in blues, R&B and early rock ‘n’ roll. But it’s also about blues artist Muddy Waters (Jeffrey Wright), R&B singer Etta James (Beyonce Knowles), rock ‘n’ roll pioneer Chuck Berry (Mos Def), virtuoso harmonica player (among other things) Little Walter (Columbus Short), blues singer/songwriter/bassist/producer Willie Dixon (Cedric The Entertainer), bluesman Howlin’ Wolf (Eamonn Walker) … have I made my point yet?

Most of these people deserve their own biopics, but in “Cadillac Records” we find nearly 30 years worth of their life stories all jammed together into 109 minutes of film. This is the film’s greatest crime: In trying to tell so many peripheral stories in the pursuit of telling Leonard Chess’ story, the film mostly just succeeds in whetting the appetite for more about the stories of this litany of Rock and Roll Hall of Fame members. There are simply so many interesting stories that the film that, because its scope is so broad and Martin has so much she wants to say, are only touched on rather than being properly explored.

Muddy Waters, Etta James, Chuck Berry, Little Walter — these are all people who could have an hour and 50 minutes dedicated to them alone. Interestingly, though the film is nominally about Leonard Chess, it succeeds more in telling the story of Waters’ journey from sharecropper to blues great to has-been to his comeback, complete with his relationship with his wife, Geneva (Gabrielle Union, doing a solid job in a limited role); his troubled relationship with his troubled friend and accompanying harmonica, Little Walter; his somewhat parasitic relationship with Leonard Chess, and so on.

Jeffrey Wright’s performance as Waters is one of the film’s greatest strengths; Wright brings depth and authenticity to his role, showing us a man who is surprised to see his station in life so suddenly elevated, but who then settles comfortably into living above his means until he starts running out of means to live above. Mostly, Muddy is a man who absorbs his setbacks with a certain stoicism; he never seems to get too worked up over rock ‘n’ roll rising up at the expense of artists like him.

Mos Def offers up a performance of note as Chuck Berry, a talented musician with the ability to unite blacks and whites to go along with a weakness for under-age girls. I recall hearing a lot of “oh no” with regard to that particular casting, and though Mos Def sure looks nothing like Chuck Berry, he does have a good enough voice to sing the songs.

I’d like to say that Knowles was a noteworthy Etta James, but her character was kind of dumped into the film in its second half, a muddled, half-explained fragment that does no justice to James’ much bigger, deeper story. Knowles’ acting is fine, though not exceptional, and if she’s a few stone lighter than the real Etta James, well, that’s open to artistic interpretation.

The section on James is emblematic of the failures of “Cadillac Records”; in too many instances, the film simply pays lip service to the artists it’s covering — James, Berry, Howlin’ Wolf and Little Walter get big, interesting sections of their lives cut out, and even the character of Leonard Chess is only superficially explored, though Adrien Brody — who looks just as out of place as his character actually is — puts on a fine portrayal.

It’s interesting to see this film labeled as a musical, since it lacks some basic elements of the musical — chiefly, the whole arbitrarily breaking into song aspect. The music in “Cadillac Records” is mostly reserved for those times when the artists are playing music for a reason, like when they’re playing a show or recording an album. This is good; launching into song for no reason would cheapen the experience.

It’s the experience that’s the most absorbing part; though the film tries to do too much, Martin is ultimately successful in setting the tone and carrying the story, jumbled though it may be, through its conclusion, such as it is. Solid acting and direction make “Cadillac Records” a very watchable film, but its lack of focus ensures that it’s more likely to make a splash at the BET Awards than the Oscars.

Yeah, I went there.
Note: Thank you to reader (I have readers?!) Elizabeth for pointing out that Darnell Martin is, despite her extremely male-sounding name, a woman. A humble mea culpa. This is what I get for not checking her Wikipedia page.