Bach's main achievement lies in his synthesis and advanced development of the primary contrapuntal idiom of the late Baroque, and in the basic tunefulness of his thematic material. He was able to successfully integrate and expand upon the harmonic and formal frameworks of the national schools of the time: German, French, Italian, and English, while retaining a personal identity and spirit in his large output. Bach is also known for the numerical symbolism and mathematical exactitude which many people have found in his music -- for this, he is often regarded as one of the pinnacle geniuses of Western civilization, even by those who are not normally involved with music.

Bach spent the height of his working life in a Lutheran church position in Leipzig, as both organist and music director. Much of his music is overtly religious, while many of his secular works admit religious interpretations on some levels. His large output of organ music is considered to be the greatest legacy of compositions for the instrument, and it is the measure by which all later efforts are judged. His other solo keyboard music is held in equally high esteem, especially for its exploration of the strictly contrapuntal fugue; his 48 preludes and fugues (The Well-Tempered Clavier) are still the primary means by which these forms are taught. His other chamber music is similarly lofty, the sets for solo violin and solo cello being the summits of their respective genres. Bach's large-scale sacred choral music is also unique in its scope and development. The St. John and St. Matthew passions and B Minor Mass led to the rediscovery of his music in the 19th century. His huge output of cantatas for all occasions is equally impressive. Finally, his large output of concerti includes some of the finest examples of the period, including the ubiquitous Brandenberg Concertos. ~ Todd McComb