Several great German musicians had called Erfurt home while Ambrosius was there, including another notable Johann: the great Pachelbel. Pachelbel also taught Sebastian's older brother Johann Christoph, with whom Sebastian lived after his parents' deaths in 1695. Erfurt was also where Martin Luther was ordained priest, and the significance of this will be discussed more in depth below.(Williams 5-9).
All these things must have had a profound effect on Bach's writing, particular his earliest works. However, there is more to add. For instance, the town of Eisenach was once the home of Martin Luther. Luther was also voluntarily imprisoned in the town castle during his time there, where he wrote his famous translation of the New Testament and possibly some of his hymns. Lutheranism and Martin Luther's close association to these two towns must have influenced Bach. He used Luther's hymns as inspiration on occasion in his compositions. (Williams 9).
In May 1694, Bach's mother died, and his father died nine or ten months later in 1695. At which point Sebastian and his elder brother Jacob moved to Ohrdruf to live with their elder brother Christophe. Prior to this, Sebastian had been a choir boy, and upon moving to Ohrdruf, Christophe either began or continued Sebastian's lessons on the keyboard. Sebastian also aided Christophe in his duties as a professional organist, copying music, tuning instruments, and the like. Christophe also passed on an interest in French organ music, which he may have acquired in his lessons with Pachelbel, to his younger brother. .
It was during Sebastian's time with his brother that he may have taught himself composition and composed his first bits of organ literature(Williams 8-9). In 1700, Bach left his brother for the town of Luneburg to attend the school at St. Michael's Church. While he was there, he sang in the choir to pay for his school and board. He also made trips to Hamburg every so often to hear the great organist Johann Adam Reinken.