Conversation so far:
What did Yip Harburg do on Broadway?
In the 1940s, Yip Harburg wrote a series of book musicals with social messages.
Was Yip Harburg a writer for Finian's Rainbow?
Yip Harburg wrote the book and lyrics for Finian's Rainbow.

Question: What did Harburg do in Hollywood?
Self-contained rewrite: What did Yip Harburg do in Hollywood?