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.