I learned something interesting from my friend Chris the code monkey this week. He said
Tonal music establishes a base, so that it means something to leave it and return, which you can hear in Bach. When you leave the base, you can feel tonal “gravity” pulling you back, and when you do come back, it’s a release of tension. There are many ways to create and release tension in music, and tonality is one way to do that, according to specific principles, with harmony.
And now you also know what “atonal” music is: music that doesn’t follow those principles for creating harmonic tension. Such music might have other rules, or create tension in some completely different way.
wow. That’s so cool!