( 'six chorales of diverse kinds, to be played on an organ with two manuals and pedal'), commonly known as the Schübler Chorales (), BWV 645–650, is a set of chorale preludes composed by Johann Sebastian Bach. Johann Georg Schübler, after whom the collection came to be named, published it in 1747 or before August 1748, in Zella St. Blasii. At least five preludes of the compilation are transcribed from movements in Bach's church cantatas, mostly chorale cantatas he had composed around two decades earlier. These six chorales provide an approachable version of the music of the cantatas through the more marketable medium of keyboard transcriptions. Virtually all Bach's cantatas were unpublished in his lifetime. Context and content The hymn tunes of the Lutheran hymns on which the chorale settings included in the Schübler Chorales are based can be identified by their Zahn number. The fourth chorale of the set is however based on a German variant of the Ninth psalm tone. Five of the Schübler Chorales are transcriptions of movements of extant church cantatas by Bach. These cantatas belong to the chorale cantata or second year cycle. Bach began to present the cantatas of this cycle from the first Sunday after Trinity 11 June 1724, which was the start of his second year in Leipzig. He continued to present 40 new chorale cantatas until Easter of the next year, 1 April 1725, from which day the chorale cantata cycle and the second year cycle no longer coincide: for the remainder of his second year in Leipzig his newly composed church cantatas were no longer in the chorale cantata format, while on the other hand he added chorale cantatas to the cycle which were composed outside the period of his second year in Leipzig. Listed according to the sequence of the liturgical year: BWV 6 is a cantata for Easter Monday: it was first presented in Bach's second year in Leipzig, on 2 April 1725, shortly after Bach had discontinued chorale cantatas in that year. Its third movement is the model for BWV 649. BWV 10 is a cantata for Visitation: this chorale cantata was presented during Bach's second year in Leipzig, on the Feast of the Visitation, 2 July 1724. Its fifth movement is the model for BWV 648. BWV 93 is a cantata for the fifth Sunday after Trinity: first presented one week after BWV 10, on 9