Conversation so far:
How long before Sarah Vaughan joined the other group of musicians?
During her week of performances at the Apollo Theatre, Sarah Vaughan met Earl Hines. After a tryout, Hines replaced his female singer with Vaughan on April 4, 1943.

Question: What year did Eckstine quit the Hines Band?
Self-contained rewrite: What year did Billy Eckstine quit the Earl Hines Band?