Are you arguing that playing music out loud is illegal?

A public performance would be in violation of civil law rather than criminal law. But if you're being pedantic you could argue that, yes, it was technically illegal.

I am not being pedantic. I don’t understand your position. It seems you are saying that the police officer is violating copyright by playing music in a public space. Whether or not ASCAP would come after me or not, is it really true that in the US I cannot play music aloud on public property?

Public performance is an exclusive right of the copyright holder as per the Berne Convention, which is signed by 179 countries.

https://www.law.cornell.edu/treaties/berne/11.html

https://en.m.wikipedia.org/wiki/Berne_Convention

Enforcement varies.

I couldn’t find a clear definition of “public performance”. Everything I found related to a bar playing a song or a cover artist playing a song for money.

You'd have to talk to a laywer. I believe it is OK as long as you're playing it for friends and family.

If you're broadcasting it electronically, like radio, it's OK as long as you have a blanket broadcast license.

Given the cop specifically asked and confirmed that there were people listening, he probably should have had a license.

Good thing, too -- if it were a criminal matter, we'd have to rely on them prosecuting themselves.

A copyrighted work, in public? Yes, very much so, and it has been for a long time.

Play a copyrighted track in your business lobby and see how long it takes ASCAP to track you down.

It is if other people can hear it and you have not licensed it.