From the listing, I thought Miles was going to be in the film improvising. It turns out it is a French film in which they still needed the music after the filming was finished. Louis Malle asked Miles Davis to improvise the music. He watched the film straight through once and then the 2nd time through, he improvised the music in one take. It was great music. There were no subtitles, so I could focus on the music and the film itself. It was also pretty easy to see what was going on without understanding the words. I saw some film of Miles watching the film and playing later at the exhibition at the Musee des Beaux Arts.
I had to leave halfway through, so I hope to get to see it again some time, preferably with subtitles. I found the 2nd half of the story from wikipedia.
The fest listing:
Ascenseur pour l'échafaud
by Louis Malle (Fr. 1957, 91 min, 35 mm, OV, Fr.)
Miles improvises for Louis Malle: an historic contribution, in
both music and cinema. With Jeanne Moreau and Maurice