From www.mutopiaproject.org

Sechs Chorale von verschiedener Art: auf einer Orgel mit 2 Clavieren und Pedal vorzuspielen, 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.
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