Schübler Chorales is a name usually given to the Sechs Chorale von verschiedener Art ('Six Chorales of Various Kinds') for organ (BWV 645–650), a collection of six chorale preludes by Johann Sebastian Bach, issued around 1748. The title 'Schübler Chorales' derives from the engraver and publisher Johann Georg Schübler, who is named on the title page. All six of the preludes are for an organ with two manuals and pedal, at least five of them transcribed from movements in Bach's cantatas, mostly chorale cantatas, as follows:

BWV	Chorale Name	Transcribed from
645	Wachet auf, ruft uns die Stimme ("Wake, Awake for Night is Passing")	Wachet auf, ruft uns die Stimme, BWV 140, movement 4 (tenor chorale)
646	Wo soll ich fliehen hin ("Whither shall I flee?")	? lost cantata (see below)
647	Wer nur den lieben Gott lässt walten ("Who allows God alone to rule him")	Wer nur den lieben Gott läßt walten, BWV 93, movement 4 (duet for soprano and alto)
648	Meine Seele erhebt den Herren ("My soul doth magnify the Lord")	Meine Seel erhebt den Herren, BWV 10, movement 5 (duet for alto and tenor, chorale instrumental)
649	Ach bleib bei uns, Herr Jesu Christ ("Lord Jesus Christ, with us abide")	Bleib bei uns, denn es will Abend werden, BWV 6, movement 3 (soprano chorale)
650	Kommst du nun, Jesu, vom Himmel herunter auf Erden ("Come thou, Jesu, from heaven to earth")	Lobe den Herren, den mächtigen König der Ehren, BWV 137, movement 2 (alto solo)

Since no source has been found for BWV 646, most scholars assume that the source cantata is one of the 100 or so believed to have been lost. The trio scoring of the movement suggests the original may have been for violin, or possibly violins and violas in unison (right hand), and continuo (left hand), with the chorale (pedal) sung by soprano or alto.

The fact that Bach had gone to the trouble and expense of securing the services of a master engraver to produce a collection of note-for-note transcriptions of this kind indicates that he did not regard the Schübler Chorales as a minor piece of hack-work, but as a significant public statement. 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 Virtually all Bach's cantatas were unpublished in his lifetime.

References

1. ^ Boyd, Malcolm. Oxford Composer Companions: J.S. Bach, Oxford University Press, 1999, p. 441–442