Primarily, the WTC is known for its pristine use of counterpoint, or multiple independent voices working together to create harmony. This is mainly seen in the

Primarily, the WTC is known for its pristine use of counterpoint, or multiple independent voices working together to create harmony. This is mainly seen in the fugues, though the preludes have plenty of it, too. In addition, Bach used this work to teach his students musical composition, and many of the pieces exemplify certain compositional techniques. For example, take a look at prelude #1. The entire piece is based on moving between chords by changing a single note, effectively demonstrating voice leading and harmony. Unfortunately, the WTC was not particularly well known during Bach's time or in the century after. If I'm remembering my music history correctly, it was barely even published during his lifetime. Eventually, it was rediscovered by the Romantic composers and has been famous ever since. I do not believe Bach actually had any hand in popularizing equal (or well) temperament. This might just be one of those legends attributed to the great composer. (We covered this in music history class when I was at university, but sadly, I don't remember the details.)