Nashville is a long (160 minutes) and quite complicated film. It requires concentration and a fair amount of patience (although I suppose one could watch it quite disinterestedly). It’s a study of a group of 25 characters, brought together into the same geographic area (Nashville TN) for the same purpose: country music, mainly making a living from it or through it.
I guess primarily its mode is documentary, as the camera follows these characters moving around. The political rally is the primary agent of the plot and structure, with many sub-orbits (Barbara Jean’s collapse, the deaf children, Sueleen’s delusion, Opal wandering around bus depots and scrapyards pondering over the American condition).
Characters interact and form molecules with each other. They don’t seem to bond much though: everyone is needy. The film meanders along in a state of constant tension and neurosis that is finally resolved by the violence and calm at its climax (Sgt Kelly and Kenny are wickedly paired together, we don’t know which will eventually go mad).