As much of a freedom as most. Freedom isn’t absolute in a majority of the cases, there are limits where it impinges on other freedom. Like you don’t have the right to park your car right in front of your neighbor’s driveway. You probably have a right to park all your cars in front of their house, but it isn’t neighborly, and they might get really mad at you and maybe key your car.
So what is the freedom we are arguing about here? Can you play music at all? Can you play music in a car if the car isn’t soundproof? Can you open your window while your music is playing? Who decides when the music has become “too loud” to be your freedom to play?
I think in general people have a right to play music in their cars, and in a place like a public parking lot, I assume I’ll hear a lot of people exercising their freedom to play music, and some of it will be loud, and maybe sometime I’ll have mine really loud because I think other people should enjoy my taste in strange music.
For example, one night after working halloween haunt, my carload pulled into a McDonalds at 1am. There were others who clearly had been at haunt, and we rolled down our windows and all started belting out one of our halloween songs we were playing on the radio. In that case, we got 3 cars full of people all screaming out the words. I imagine someone who was in the parking lot was probably disturbed, and can only be thankful we didn’t all get shot.
You have the right to free speech, but you don’t have a right to be heard.