The Umbrellas of Cherbourg (1964) IMDb
The version I saw looked like it could have used a restoration for colour, and the director could not resist genre-appropriate close-ups, even when this completely gives away the actors’ poor lip syncing. The way the Algerian conflict is woven into the musical drama is also quite disturbing; the colonial suffering of Algerians has absolutely no narrative weight next to the romantic tragedy. Still, the all-singing style is preferable to more typical, intermittent musicals like Mary Poppins (1964).
References here: Memories of Matsuko (2006).