Johann Sebastian Bach (31 March 1685 - 28 July 1750) was a composer of the Baroque era, the most celebrated member of a large family of north German musicians. While his contemporaries admired him mainly as a gifted harpsichordist, organist, and organ builder, Bach is now widely regarded as one of the greatest composers of all time, best known for the Brandenburg Concertos, The Well-Tempered Clavier, the Mass in B Minor, and numerous other works of the church and instrumental music. Bach appeared at a reasonable time in music history, allowing him to survey and put together the significant styles, forms, and national traditions that had evolved over previous centuries, enriching them all through his synthesis. He came from a distinguished family of musicians who were proud of their accomplishments. In about 1735, Bach compiled a genealogy, Ursprung der musicalisch-Bachischen Familie ("Origin of the Musical Bach Family"), in which he traced his ancestry back to his great-great-grandfather Veit Bach, a Lutheran baker (or miller) who was driven from Hungary to Wechmar in Thuringia, a Saxon town, late in the 16th century. There had been Bachs in the region before that. Veit was said to be returning to his birthplace when he moved to Wechmar. He used to go to the mill with his cittern and play it when it was grinding. He did, however, learn to keep time, and this seems to be the start of music in our family." Before the birth of Johann Sebastian, his family branch had been the least illustrious; some of its members, such as Johann Christoph and Johann Ludwig, were capable performers but not composers. Johann Sebastian's sons—Wilhelm Friedemann, Carl Philipp Emanuel, and Johann Christian (the "English Bach")—were the family's most influential musicians in later years.

The young Bach excelled at school once more, and in 1700, his voice earned him a place in a select choir of poor boys at the Michaelskirche school in Lüneburg. His voice must have broken soon after, but he stayed in Lüneburg for a while, proving himself useful in various ways. He studied in the school library, which had a comprehensive and current collection of church music; he most likely heard Georg Böhm, organist of the Johanniskirche. In addition, he most likely heard Johann Adam Reinken, renowned organist and composer, at the Katharinenkirche and the French orchestra maintained by the duke of Celle. In the late summer of 1702, Bach seems to have returned to Thuringia. He was already an accomplished organist at this stage. His time in Lüneburg, if not Ohrdruf, had driven him away from his immediate ancestors' secular string-playing heritage, and he became primarily, but not exclusively, a composer and performer of keyboard and sacred music. The next few months are shrouded in mystery. However, by March 4, 1703, he was a member of Johann Ernst, Duke of Weimar's orchestra (and brother of Wilhelm Ernst, whose service Bach entered in 1708). He certainly already had his eye on the organ installed at the Neue Kirche (New Church) in Arnstadt. He helped to test the organ when it was completed. In August 1703, he was appointed organist—all of this at 18. Arnstadt documents imply that he had been court organist at Weimar; this is incredible, though it is likely enough that he had occasionally played there. Bach's six Cello Suites (BWV 1007–1012) were most likely composed around 1720 when he was employed at the Cöthen court. While having the same form (a prelude followed by five movements centered on courtly dance rhythms), each of the six suites has its personality.