See article “Quodlibet” in Grove.
The date is conjectural, and is deduced from the fact that the infant was baptized on March 23. The Gregorian Calendar was not adopted in Germany until 1701. Had it been in use in 1685 Bach's birthday would be March 31.
Johann Ambrosius' Court appointment is to be inferred from the fact that in 1684 the Duke refused him permission to return to Erfurt.
See Table IV.
Johann Ambrosius survived his brother by nearly eighteen months.
His mother died in May 1694, and his father in January 1695. At the latter date Johann Sebastian was three months short of his tenth year.
Excepting Johann Jakob, a lad of thirteen years, Johann Christoph was Bach's only surviving brother, and the only one of the family in a position to look after him. Johann Jakob accompanied Sebastian to Ohrdruf (Pirro, p. 13) and afterwards apprenticed himself to his father's successor as Town Musician at Eisenach. One of the daughters was already married. What became of the other is not stated. See Table V.
It is difficult to believe this statement. That the boy was destined for a musical career by his father hardly can be doubted. That he was of unusual precocity, the story told by Forkel in the text proves. His father's asserted neglect to instruct him is therefore hardly credible.
Johann Jakob Froberger, born at Halle (date unknown); Court Organist at Vienna, 1637-57; d. 1667.
Johann Caspar Ferdinand Fischer, c. 1660-1738 (actual dates of his birth and death unknown); Kapellmeister to Markgraf Ludwig of Baden at Schloss Schlackenwerth in Bohemia. His Ariadne Musica Neo-Organoedum (1702) was the precursor of Bach's Das wohltemperirte Clavier.