The normal way you play music is for your own enjoyment. It's incidental if other people overhear. He said that wasn't what he did.
The harmed party needs to be the owner of the copyright, because people listen to this instead of paying them.
Unauthorized public performance is a violation of the copyright holder's exclusive rights. Market effect is only 1 of several factors examined together for a fair use defense.
They have no reason to sue this guy that doesn't apply to millions of other cases that happen every day.
