I listen to both classical and rock music in the car, but usually one kind per trip; I'm either in a classical mood or a "wake me up, dammit" mood. So I was having a classical mood, but then the announcer said "next up: Greensleeves!"
I said "Oh HELL no" and changed the channel to a rock station.
And here's where the interesting thing happened: I heard only NOISE for about five seconds, and then it gradually resolved into music - and it was even a song I knew and liked!
It seems the brain has different programs running to interpret different kinds of music, and it takes time to switch from one to the other. This led to two subsequent realizations:
When old fogeys say "This newfangled stuff you call music is just noise!" they're RIGHT! They don't have the programming to parse it into actual music. (And the young kids don't have the programming for classical, so it doesn't sound right to them either.) I don't know if it takes training or just repeated exposure to instill programming for a particular musical type - probably just exposure.
The other realization was of a more personal nature. I listened to classical music almost exclusively growing up, with the exception of a couple of pop albums when I was 11 or 12. The first rock music that I truly became a fan of was PInk Floyd. The realization was that PInk Floyd often uses progressive layering to begin their songs, gradually becoming more complex until the thing kicks off in earnest. Time is a good example. Pink Floyd was, in effect, training my brain to be able to understand how it is put together, making it an extremely effective gateway drug when it came to me and progressive rock.