The role of Linnea Reese was created for and by Louise Fletcher, who herself was the daughter of two deaf parents and knew sign language. The role was eventually played by Lily Tomlin. Tomlin concluded that things worked out in the end because she was offered the role of Nurse Ratched in One Flew Over the Cuckoo's Nest (1975) and turned it down, which enabled Fletcher to eventually get it, so in a sense they simply traded roles.
After seeing the first footage of her work in the traffic jam scene, Barbara Harris reportedly ran out of the projection room, went home, and asked Robert Altman to meet with her immediately. Unhappy with her performance, Harris offered to put up her own money to have the scene re-shot. Altman told her no.
Robert Altman originally wanted Susan Anspach to play Barbara Jean, but she refused because she wanted more money. Ready to film in Nashville with no one cast in the role, Altman at the last minute offered it to Ronee Blakley, who was working as a back-up singer in Nashville at the time and had contributed some songs to the film. Blakley ended up receiving an Academy Award nomination for her performance.
In the opening sequence, the character played by Henry Gibson demanded that his piano player be replaced by the "Pig". At that time in Nashville, one of the most in-demand session players was a blind pianist named Hargus "Pig" Robbins. The man playing the piano in that scene is Richard Baskin, the actual music supervisor on the film.
The film was created due to an offer Robert Altman turned down. Originally, he was offered the chance to direct another script that took place in Nashville. He turned the project down but became interested in the setting. He sent his script supervisor, Joan Tewkesbury, to Nashville to observe the place and take notes. She wrote a diary and that diary became the basis of her screenplay. From there, several scenes were rewritten or improvised by the performers, a standard practice on Altman projects.
In response to those who believed the film was almost totally improvised and had little or no script, screenwriter Joan Tewkesbury insisted that there was a solid script written by Robert Altman and herself that dictated all the actions of all the characters, and that the improvisational elements added by the actors were solely in aspects of the dialogue.
During the DVD commentary of the film, Robert Altman pays a tribute to Tommy Thompson, who was the assistant director on almost all of Altman's films, and who had dropped dead on the set of Dr. T and the Women (2000) a week before Altman did the commentary.
Robert Duvall was originally offered the role of Haven Hamilton but had a scheduling conflict and was unable to do so. As a result, he was replaced by Henry Gibson. In commenting on the movie, Robert Altman has said that the movie would certainly have been different with Duvall in the role, but he was happy with Gibson playing the part. Duvall later went on to perform his own compositions in Tender Mercies (1983) as part of his Oscar-winning turn as country music singer Mac Sledge.
Award winning fiddler and actor Johnny Gimble makes a cameo appearance during the last big stage scene when he does a 'walk on' with his fiddle and joins fiddler Vassar Clements and the rest of the band as they perform.
The trivia items below may give away important plot points.
Faced with an impending rainstorm which threatened to ruin filming of Barbara Jean's assassination (with no recourse, as the production's budget had run dry), Robert Altman reportedly screamed at the sky, ordering the rain to stop. The rain did indeed stop, and filming of the scene was completed.