Lee Marvin drank real alcohol throughout the production, even though director Joshua Logan fought him about it. In most movies, the actors and actresses drink tea for whiskey and water for vodka. Marvin would only work if he got real liquor.
Jean Seberg's singing voice was dubbed by Anita Gordon. Clint Eastwood and Lee Marvin did their own singing. Marvin's recording of the song "Wanderin' Star" went to number one on the U.K. charts, earning him a gold record.
Jean Seberg (Elizabeth) described Lee Marvin's (Ben Rumson's) singing as "like rain gurgling down a rusty pipe".
In his memoir, Alan Jay Lerner relates that Anita Gordon, his first choice to dub Jean Seberg's singing, had faded from view by 1969, as the studio system had dissolved and movie musicals were rarely produced. But he was convinced that Gordon was the best match for Seberg's speaking timbre. When all of his attempts to locate the elusive Gordon failed, he contacted the Screen Actors Guild in one final attempt to track her down. When Lerner told the phone operator at SAG that he was seeking a singer named Anita Gordon, he received a shock when the operator responded that she herself was Anita Gordon. And, with that, Miss Gordon played her final hand in Hollywood as Seberg's voice double.
Alan Jay Lerner: Singing while standing on the log next to William O'Connell during "There's a Coach Coming In."