The measuring stick for movies about musical groups is "The Commitments." "The Sapphires" doesn't quite hit that lofty standard, but it's nevertheless a thoroughly entertaining ride.
Three aboriginal (Australian) sisters go into town to play at a talent show. Problem is, this is 1968 and aboriginals aren't considered fully human (a fact made clear by text on screen before the movie starts). They're the best group, but lose the contest anyway. The drunken Irish M.C. Dave (Chris O'Dowd) helps them get an audition to go play for troops in Vietnam. They're joined by their fair-skinned cousin who the government had taken away to be raised in a white family, and after some rehearsal, they successfully audition.
What this description leaves out is the ... hmmm, "plain speaking" favoured by the sisters. And the drunken obnoxiousness of Dave. The music is pretty good, and it's a very funny movie. I remember some friends of mine liked this when it was released, but it's quietly disappeared since: it deserved a better fate. Go watch it.