Perhaps no man ever led a more crowded life, though outwardly a quiet one.  He never had an idle moment.  When not playing, composing or teaching, he would be found engraving music on copper, since that work was costly in those days.  Or he would be manufacturing some kind of musical instrument.  At least two are known to be of his invention.

Bach began to realize that the Coethen post, while it gave him plenty of leisure for his work, did not give him the scope he needed for his art.  The Prince had lately married, and did not seem to care as much for music as before.

The wider opportunity which Bach sought came when he was appointed director of music in the churches of St. Thomas and St. Nicholas in Leipsic, and Cantor of the Thomas-Schule there.  With the Leipsic period Bach entered the last stage of his career, for he retained this post for the rest of his life.  He labored unceasingly, in spite of many obstacles and petty restrictions, to train the boys under his care, and raise the standard of musical efficiency in the Schule, as choirs of both churches were recruited from the scholars of the Thomas School.

During the twenty-seven years of life in Leipsic, Bach wrote some of his greatest works, such as the Oratorios of St. Matthew and St. John, and the Mass in B Minor.  It was the Passion according to St. Matthew that Mendelssohn, about a hundred years later discovered, studied with so much zeal, and performed in Berlin, with so much devotion and success.

Bach always preferred a life of quiet and retirement; simplicity had ever been his chief characteristic.  He was always very religious; his greatest works voice the noblest sentiments of exaltation.

Bach’s modesty and retiring disposition is illustrated by the following little incident.  Carl Philip Emmanuel, his third son, was cembalist in the royal orchestra of Frederick the Great.  His Majesty was very fond of music and played the flute to some extent.  He had several times sent messages to Bach by Philip Emmanuel, that he would like to see him.  But Bach, intent on his work, ignored the royal favor, until he finally received an imperative command, which could not be disobeyed.  He then, with his son Friedmann, set out for Potsdam.

The King was about to begin the evening’s music when he learned that Bach had arrived.  With a smile he turned to his musicians:  “Gentlemen, old Bach has come.”  Bach was sent for at once, without having time to change his traveling dress.  His Majesty received him with great kindness and respect, and showed him through the palace, where he must try the Silbermann pianofortes, of which there were several.  Bach improvised on each and the King gave a theme which he treated as a fantasia, to the astonishment of all.  Frederick next asked him to play a six part fugue, and then Bach improvised one on a theme of his own.  The King clapped his hands, exclaiming over and over, “Only one Bach!  Only one Bach!” It was a great evening for the master, and one he never forgot.