Miles Davis recorded the music in a single recording session while he watched a screening. He composed it while watching a rough cut and then invited a quartet of French and US musicians in a for few hours (from 11pm to 5am one night), improvising each number and allegedly sipping champagne with Jeanne Moreau and Louis Malle.
Louis Malle shot his lead actress Jeanne Moreau in close-up and natural light and often without make-up. Moreau, an icon of French film, had never been seen like this before, to the extent that lab technicians, reportedly appalled at how unflatteringly she was photographed, refused to process the film. Once they were persuaded to, however, it soon began clear that Malle had captured every nuance of Moreau's performance.
The tiny camera is a Minox. It was originally developed as a luxury item, but it gained notoriety from its use as a spy camera.
The scene of Florence walking down the Champs Elysees at night was shot using fast film in a camera mounted on a baby carriage and used only natural light from the street and store windows.