The animation of the characters dancing in "The Jungle Book" (1967), was created based on video of the musicians, Louis Prima and his band, performing this number:
https://www.youtube.com/watch?v=rV8HrpOu1FA
I can sort of see why Jazz on a Summer's Day is missing, but it's a shame since it defined the style of almost every festival film that followed.
I dont know these movies and Le Départ (1967) is missing. Everytime I hear Jazz I think about Jean-Pierre Leaud driving around on white Vespa.