Conversation so far:
What was Billy Joel doing musically in 1965?
Billy Joel joined the Echoes, a group that specialized in British Invasion covers. The Echoes began recording in 1965.
What was the name of the first recording by the Echoes?
Did the Echoes do mostly covers?
Billy Joel joined the Echoes, a group that specialized in British Invasion covers.
What did Billy Joel do after being in The Echoes?
Billy Joel joined the Hassles, a Long Island group that had signed with United Artists Records, in 1967.
What style of music did Billy Joels's The Hassles play?
The Hassles were a rock group.
What was the Hassles' first record?
The Hassles released four singles and two albums (The Hassles and Hour of the Wolf).
Did the Hassles have any success with those records?
The four singles and two albums (The Hassles and Hour of the Wolf) released by The Hassles were all were commercial failures.

Question: When did he leave The Hassles?
Self-contained rewrite: When did Billy Joel leave The Hassles?