I'd go to the police, explain that you heard x number of songs in a row blaring that played in the exact order they are on your play list. Tell them you asked the guy about it, and how he played coy, even denying he heard any music at all.
And my guess is the police won't investigate.
So, that leave you where? Well, if you don't do something, I worry things are going to escalate. They will see they can get away with victimizing you in this way, something they clearly are enjoying doing with impunity -- so it will get worse.
If the police won't help you, I'd say your options are to be safe, you'd better move, or do something yourself.
Of course, I would never advise taking the law into one's own hands or breaking the law. Someone in your position should resist the temptation to react, even doing in relative safely, by ensuring the bad guys are vastly outnumbered. And you should definitely not go in there with a group of people and recover your property, and exact your revenge using violence and or threats.
Seriously, if it were me, I'd go to the police, but I can tell you our police have a national reputation for being allergic to investigating and to laying charges, unless there is high definition video surveillance tape.
If you get no help from them, you're in the position of what the heck do you do. The awful dilemma is this. If you act in proportion to the offense, you are vulnerable to escalating "retaliation." There's a pretty limited range of things you can do that would preclude such vulnerability -- that is, taking extreme action. That is truly troubling to contemplate. Either you commit an uncalled for atrocity, or risk suffering one.
I would start with going to the police, don't call, go in person.
You're not friends with a biker gang, by chance?