Conversation so far:
How did Herb's music career begin?
Jeffries began his career working with Erskine Tate and his Vendome Orchestra.
What year was that?
His break came during the 1933 Chicago World's Fair A Century of Progress International Exposition singing with the Earl Hines Orchestra.

Question: What did he gain with his big break?
Self-contained rewrite: What did Jeffries gain with his big break?