Great Eighteen Chorale Preludes
The works form an encyclopedic collection of large-scale chorale preludes, in a variety of styles harking back to the previous century, that Bach gradually perfected during his career.
Together with the Orgelbüchlein, the Schübler Chorales, the third book of the Clavier-Übung and the Canonic Variations, they represent the summit of Bach's sacred music for solo organ.
As his son Carl Philipp Emanuel Bach mentions in his obituary or nekrolog: "His grace's delight in his playing fired him to attempt everything possible in the art of how to treat the organ.
The autograph manuscript of the Great Eighteen, currently preserved as P 271 in the Berlin State Library, documents that Bach began to prepare the collection around 1740, after having completed Part III of the Clavier-Übung in 1739.
In 1750 when Bach began to suffer from blindness before his death in July, BWV 666 and 667 were dictated to his student and son-in-law Johann Christoph Altnikol and copied posthumously into the manuscript.
The piece, however, is now accepted as a planned reworking of the shorter chorale prelude Wenn wir in höchsten Nöthen sein (BWV 641) from the Orgelbüchlein (c 1715).
"[13] The eighteen are characterized by their freely developed and independent accompaniment filling the long intervals between the successive lines of the cantus firmus, a feature of their large scale which has not pleased all commentators.
This style goes back to the Dutch composer Sweelinck and was adopted by his German pupils Scheidt and Scheidemann; the tradition was continued at the turn of the 18th century by Georg Böhm and Pachelbel from Thuringia, who provided the model for Bach.
This might be a homage to Dieterich Buxtehude, who had written similar partitas and whose music and virtuosity at the organ is known to have exercised a considerable influence on Bach in his youth.
Bach elevated this form to the status of contemporary Italian trio sonatas or double concertos of Antonio Vivaldi and Giuseppe Torelli: it is probably his single most original innovation in the repertoire of organ chorales.
