Johann Sebastian Bach^[1] (21 March 1685, O.S.^{31 March 1685, N.S.} – 28 July 1750, N.S.) was a German composer, organist, harpsichordist, violist, and violinist whose sacred and secular works for choir, orchestra, and solo instruments drew together the strands of the Baroque period and brought it to its ultimate maturity.^[2] Although he did not introduce new forms, he enriched the prevailing German style with a robust contrapuntal technique, an unrivalled control of harmonic and motivic organisation, and the adaptation of rhythms, forms and textures from abroad, particularly from Italy and France.

Revered for their intellectual depth, technical command and artistic beauty, Bach's works include the Brandenburg Concertos, the Goldberg Variations, the Partitas, The Well-Tempered Clavier, the Mass in B minor, the St Matthew Passion, the St John Passion, the Magnificat, the Musical Offering, The Art of Fugue, the English and French Suites, the Sonatas and Partitas for solo violin, the Cello Suites, more than 200 surviving cantatas, and a similar number of organ works, including the famous Toccata and Fugue in D minor and Passacaglia and Fugue in C minor, and the Great Eighteen Chorale Preludes and Organ Mass.

Bach's abilities as an organist were highly respected throughout Europe during his lifetime, although he was not widely recognised as a great composer until a revival of interest and performances of his music in the first half of the 19th century. He is now generally regarded as one of the main composers of the Baroque style, and as one of the greatest composers of all time.^[3]

Johann Sebastian Bach was born in Eisenach, Saxe-Eisenach, on 21 March 1685, O.S.^{31 March 1685, N.S.}. He was the youngest child of Johann Ambrosius Bach, the director of the town musicians,^[4] and Maria Elisabeth Lämmerhirt. His father taught him to play violin and harpsichord.^[5] His uncles were all professional musicians, whose posts ranged from church organists and court chamber musicians to composers. One uncle, Johann Christoph Bach (1645–93), introduced him to the art of organ playing. Bach was proud of his family's musical achievements, and around 1735 he drafted a genealogy, "Origin of the musical Bach family".^[6]

Bach's mother died in 1694, and his father eight months later.^[7] The 10-year-old orphan moved in with his oldest brother, Johann Christoph Bach (1671–1721), the organist at the Michaeliskirche in Ohrdruf, Saxe-Gotha-Altenburg.^[8] There, he copied, studied and performed music, and received valuable teaching from his brother, who instructed him on the clavichord. J.C. Bach exposed him to the works of the great South German composers of the day, such as Johann Pachelbel (under whom Johann Christoph had studied)^[9] and Johann Jakob Froberger, to the music of North German composers;^[10] to Frenchmen, such as Jean-Baptiste Lully, Louis Marchand, Marin Marais, and to the Italian clavierist Girolamo Frescobaldi. The young Bach probably^{[clarification needed]} witnessed and assisted in the maintenance of the organ music. Bach's obituary^[11] indicates that he copied music out of Johann Christoph's scores, but his brother had apparently forbidden him to do so, possibly because scores were valuable and private commodities at the time.^[12]

At the age of 14, Bach, along with his older school friend George Erdmann, was awarded a choral scholarship to study at the prestigious St. Michael's School in Lüneburg in the Principality of Lüneburg.^[13] This involved a long journey with his friend, probably^{[clarification needed]} undertaken partly on foot and partly by coach. His two years there appear to have been critical in exposing him to a wider facet of European culture. In addition to singing in the a cappella choir, it is likely^{[clarification needed]} that he played the School's three-manual organ and its harpsichords. He probably^{[clarification needed]} learned French and Italian, and received a thorough grounding in theology, Latin, history, geography, and physics. He would have come into contact with sons of noblemen from northern Germany sent to the highly selective school to prepare for careers in diplomacy, government, and the military.

Although little supporting historical evidence exists at this time, it is almost certain that while in Lüneburg, young Bach would have visited the Johanniskirche (Church of St. John) and heard (and possibly played) the church's famous organ (built in 1549 by Jasper Johannsen and nicknamed the "Böhm organ" after its most prominent master, Georg Böhm). Given his innate musical talent, Bach would have had significant contact with prominent organists of the day in Lüneburg, most notably Böhm (the organist at Johanniskirche) as well as organists in nearby Hamburg, such as Johann Adam Reincken.^[14]

In January 1703, shortly after graduating from St. Michael's and after having failed an audition for the post of organist at Sangerhausen,^[15] Bach gained an appointment as a court musician in the chapel of Duke Johann Ernst in Weimar. His role there is unclear, but appears to have included menial, non-musical duties. During his seven-month tenure at Weimar, his reputation as a keyboard player spread. He was invited to inspect and give the inaugural recital on the new organ at St. Boniface's Church in Arnstadt.^[16] The Bach family had close connections with people in this ancient town located about 40 km to the southwest of Weimar.^[17] In August 1703, he accepted the post of organist at that church, with light duties, a relatively generous salary, and a fine new organ tuned in the modern tempered system that allowed a wide range of keys to be used. At this time, Bach was embarking on the composition of organ preludes; these works, in the North German tradition of virtuosic, improvisatory preludes, already showed tight motivic control (in which a single, short musical idea is explored throughout a movement). In these works the composer had yet to fully develop his powers of large-scale organisation and contrapuntal technique.

Strong family connections and a musically enthusiastic employer failed to prevent tension between the young organist and the authorities after several years in the post. Bach was apparently dissatisfied with the standard of singers in the choir; more seriously, there was his unauthorised absence from Arnstadt for several months in 1705–06, when he visited the great organist and composer Dieterich Buxtehude and his Abendmusiken at the Marienkirche in the northern city of Lübeck. The visit to Buxtehude involved a journey on foot of about 400 kilometres (250 mi) each way. The trip reinforced Buxtehude's style as a foundation for Bach's earlier works, and that he overstayed his planned visit by several months suggests that his time with the older master was of great value him. Bach wanted to become amanuensis (assistant and successor) to Buxtehude, but did not want to marry his daughter, which apparently was a condition for his appointment.^[18]