Cameo: [Giorgio Moroder] radio station executive at the very end.
The cello piece played by Madeline in the song "The Duel" is the Minuet #4 in G (BWV Anh.II.114) from "Notebook for Anna Magdalena Bach" by Christian Petzold (formerly attributed to Johann Sebastian Bach).
As the voice of the computer, Bud Cort had to deliver his entire performance from inside a box on the set; his co-stars were never allowed to see him during filming. The director was afraid that if the other performers associated a person to the voice, they would react to it as if they were talking to a human being instead of a computer and the difference in reaction would show on camera.