The Importance of the Well Tempered Clavier

When Bach wrote "The Well Tempered Clavier" he wrote 24 pieces, one in each key, major and minor, which was essentially to prove that wonderful, characterful music COULD be composed in EVERY key, and people had nothing to fear from Well-Tempered instruments. By and large he succeeded, and nowadays everything is well-tempered, (in fact, "equal temperament", a slightly more advanced specific well-tempered tuning system that takes the idea to its most functional and efficient solution), and to our ears older tuning systems just sound horrible and out of tune. You could say Bach changed the world, and further you could say that he changed our ears in such a way that something old sounded ugly where once it had been beautiful.