Conversation so far:
When did Dion DiMucci begin his solo career?
In October 1960, Dion decided to quit the Belmonts for a solo career.
Why did Dion DiMucci leave the Belmonts?
There were musical, personal and financial differences between Dion and members of the Belmonts.

Question: What was a single he had?
Self-contained rewrite: What was a single Dion DiMucci had?