"To Johann Sebastian Bach, students of piano playing owe more than to any other composer of the Baroque period. Before his time, owing to the system of tuning, it was possible to play in only a limited number of keys. Bach, who had always tuned his own clavier, devised the "Tempered Scale" system of tuning which made it possible to play with equal ease in all major and minor keys. Then he composed his famous Well-Tempered Clavier (two volumes of Preludes and Fugues written in each major and minor key). He also introduced a systematic use of the thumb-a custom not observed before-which greatly increased technical possibilities of keyboard instruments."
Upon further inspection, it turned out to be a very informative passage. We learn the origins of the Well-Tempered Clavier. We may wish to engage in further readings and learn of the means by which J.S. Bach invented such system(s).
My readings have (unfortunately) not gone very far as I am engaged at the moment in preparation for my music exam and research for a term paper due when I resume classes. I was quite joyful in my discovery of this snippet; it was much more concise than those books ever shall be. To my dismay, the ABRSM 6th Grade Piano Exam does not include any selections from J.S. Bach this year. So far, I have chosen Handel's Allegro and Cecile Chaminade's Elegie, sensible, pleasant pieces, but somewhat not as enjoyable as an afternoon of Bach. In self-consolation, I continue to work on Prelude and obstinately hide Beethoven in the closet.