Ideally, a song should contain both elements of high melodic tension, and low melodic tension. No listener wants to sit through a totally high-energy… - Andrew Sega

I try to avoid categorizing music as much as I can, though. Everyone steals so much from everyone else these days, the lines between genres are very washed-out.

Imagine presenting a Nirvana or BT track to someone from the 1850's, they would probably see it as noise and not much else. Society as a whole has a much more nuanced and wide view of what music can be now. It still usually contains various rhythmic, melodic, and vocal components, but they can be combined in so many interesting ways now.

Religion is a simplistic answer that society has created in order to make people feel better, but there is little evidence as to its validity. There are thousands of religions in the world, each with their own "correct" answers, and each contradicting each other. For now the most sensible explanation to me is that we are the result of a lucky combination of cosmic factors, we're the "mold" that has grown on this particular planet and in a universe as vast as ours, it's expected that somewhere this would happen.