Complex sentence: After leaving school he tried three trades (shoe cutting, neck tie cutting and paper hanging) in quick succession but having a good tenor voice he decided on show business, in a travelling "medicine show", then a minstrel troupe before going on stage.
Split into simpler sentences: After leaving school he tried three trades (shoe cutting, neck tie cutting and paper hanging) in quick succession but he had a good tenor voice, so he decided on show business. He appeared in a travelling "medicine show", then a minstrel troupe before going on stage.