MaxQ states:
: he (Howard Goodall) had sold me a pup with his statement that J.S. Bach's "The Well-Tempered Clavier" was largely responsible for our "equal temperament" systemA pup, indeed. Yap, yap!
Faldage commented:
It certainly led the way.Well, yes and no. By the time Bach swung into action, the well-tempered tuning system had been largely developed - pretty much during the previous century, if my memory of musical history serves me correctly. Most of the work was actually done in Germany, I believe. Anyway, it was the development of the theory of the Pythagorean comma (largely playing it by ear?

) which led to the well-tempered approach used by Bach (and which sounds a
little out of key to our ears). Further refinement led to the equal-tempered system we use today.