Nobody worries about historical accuracy when making a biopic, especially about musicians. Take for ex: Cadillac Records (2008).
It stars Adrian Brody as Leonard Chess, founder of legendary Chicago blues label Chess Records. Now, if you know Chess, you might be wondering, what about his brother Phil? Well, he's not in this movie, at least he doesn't have any lines. Leonard is a Jewish immigrant of little means who wants his future wife to drive a Cadillac. He thinks he can get there by recording "race" records.
He finds talent like Muddy Waters (Jeffery Wright), Little Walter (Columbus Short), Howlin' Wolf (Eamonn Walker), Chuck Berry (Mos Def), Willie Dixon (Cedric the Entertainer) and significantly, Etta James (Beyonce Knowles). He recorded their records and got them played on the radio (even if it took a little payola). He got them all Cadillacs, but he took it out of their royalties. The message seemed to be that he was really on the artists side, but was a bit sleazy too. Also, he was faithful to his Jewish wife, except for a little thing with Etta James.
About that - he was bringing her around when she was overdosing on heroin, which progressed to the start of an intimate act. Now pardon me if I seem old-fashioned, but you don't sleep with passed-out drunks and you don't do it with someone high on smack. Gross! Sorry, had to get it off my chest.
Anyway, the historical accuracy is negligible. Fine, what about the music? Amazingly, the actors did their own singing (except Beyonce - she did her own singing and it is amazing, but it's not amazing that she did her own singing). Wright sing a solid Muddy, but he plays the role as a man unsure of himself, worried about his popularity. Eamonn Walker, on the other hand, makes an amazing Howlin' Wolf, tall with a sharp haircut and bowtie, full of righteous independence, performing a fierce rendition of "Smokestack Lightning". Mos Def isn't bad as Berry, either.
But Beyonce was best, and they save my favorite Etta James song for last, "I Would Rather Go Blind". Really, I would have liked to see a lot more of her and Howlin' Wolf, and less melodrama. Although, I did kind of the like the idea that Muddy's band were called the Head Hunters - They'd go after other bands and blow them off the stage, either with the blues or with Little Walter's gun.
In conclusion, silly story, good acting, great music.