Von Gott will ich nicht lassen - BWV 658 (God does not want to be separated, De Dieu, je ne veux pas me séparer, Da Dio non voglio separarmi).
The Great Eighteen Chorale Preludes (or rather, the autograph of Leipzig, because the manuscript was found there), or even eighteen chorales BWV 651-668 different species are a series of eighteen chorale preludes for organ by Johann Sebastian Bach in Leipzig in his last decade of life, between 1740 and 1750 from other pieces written previously in Weimar, where Bach was court organist. The work forms an encyclopedic collection of large chorale preludes in a variety of style that takes into account all of the previous century. Together all'Orgelbüchlein, the Choral Schübler and the third part of the Clavier-Übung, represent the epitome of sacred music for organ by Bach.
- from Wikipedia
in "Attachments" you can download the musical score free