Just want to add what I have noticed about music - most people, when hear a song, tell you "I know this song, it's cool" or "I don't know this song, play something else". So what I have seen fits to what you observed - people don't like songs they haven't heard of. This is maybe because we don't want to differ from other people and we subconsciously know that if we haven't heard of a song then our friends don't like it, so we should not like it, too.

And I give example with chalga music - people who dislike chalga often happen to ask "Is this chalga?". When you say "yes" they would say they don't like the song. So listening to the song itself is not enough for them to decide whether they like it or not.

Is this like that in other countries, or again we Bulgarians are different?