Conversation so far:
Where did they film?
Paris.
How was the weather during filming?
The weather had become unseasonably hot, and working in unair-conditioned hotel rooms was uncomfortable.
Where did they film?
California, where several interior scenes were filmed.
Did they like filming in California?
unhappy with the look of the scene as it had been shot by Minnelli, and at considerable expense.
When were they able to finish the score?
By mid-July, the composers had completed most of the score, but still were missing the title tune.

Question: Is there any other interesting information?
Self-contained rewrite: Besides the score Is there any other interesting information about Gigi (1958 film)?