Conversation so far:
What did Phil Hartman do in his early career?
Working alone as a graphic artist, Phil Hartman frequently amused himself with flights of voice fantasies.
What did Phil Hartman do as a graphic artist?
After graduating from California State University, Northridge with a degree in graphic arts, Phil Hartman designed album covers for bands including Poco and America.

Question: What were the voices he did to amuse himself?
Self-contained rewrite: What were the voices Phil Hartman did to amuse himself while working as a graphic artist?