Conversation so far:
what year was Gigi released?
In March 1957, the duo began working in Paris.
who developed the main character?
so Lerner agreed to write the screenplay only.
He and Freed discussed casting.
how did they pick the cast?
He and Freed discussed casting; Lerner favored Audrey Hepburn, who had starred in the Broadway production written by Loos.
how did they choose the location?
He decided to approach Loewe once again, and when he suggested they compose the score in Paris, Loewe agreed.

Question: how did they come up with the score development?
Self-contained rewrite: How did Lerner and Freed come up with the score development for the film Gigi?