Conversation so far:
What was Billy Joel doing musically in 1965?
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?
Joel played on a demo version of "Leader of the Pack".
Did they do mostly covers?
Joel states that in 1964 he played on a recording of the Shangri-Las' "Remember (Walking in the Sand).
What other songs did The Echoes do?
CANNOTANSWER.
What did he do after being in The Echoes?
Joel left the band in 1967 to join the Hassles, a Long Island group that had signed with United Artists Records.

Question: What style of music did The Hassles play?
Self-contained rewrite: What style of music did The Hassles play?