Johann Sebastian Bach ( ) (31 March 1685 – 28 July 1750) was a German composer and organist 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. Although he introduced no new forms, he enriched the prevailing German style with a robust contrapuntal technique, an unrivalled control of harmonic and motivic organisation in composition for diverse instrumentation, and the adaptation of rhythms and textures from abroad, particularly 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 Suites, the French Suites, the Sonatas and Partitas for violin solo, the Cello Suites, more than 200 surviving cantatas, and a similar number of organ works, including the celebrated Toccata and Fugue in D Minor.

While Bach's fame as an organist was great during his lifetime, he was not particularly well-known as a composer. His adherence to Baroque forms and contrapuntal style was considered "old-fashioned" by his contemporaries, especially late in his career when the musical fashion tended towards Rococo and later Classical styles. A revival of interest and performances of his music began early in the 19th century, and he is now widely considered to be one of the greatest composers in the Western tradition.

Childhood (1685–1703)

Johann Sebastian Bach was born in Eisenach, Saxe-Eisenach. He was the youngest child of Johann Ambrosius Bach, the director of the Stadtpfeifer or town musicians, and Maria Elisabeth Lämmerhirt. His father taught him to play violin and harpsichord. 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), was especially famous and 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".

Bach's mother died in 1694, and his father eight months later. The 10-year-old orphan moved in with his oldest brother, Johann Christoph Bach (1671–1721), the organist at the Michaeliskirche in nearby Ohrdruf. There, he copied, studied and performed music, and apparently 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) and Johann Jakob Froberger; possibly to the music of North German composers, to Frenchmen, such as Jean-Baptiste Lully, Louis Marchand, Marin Marais; and to the Italian clavierist Girolamo Frescobaldi. The young Bach probably witnessed and assisted in the maintenance of the organ music. Bach's obituary 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.