Several years after his appointment in 1723 as cantor of the St Thomaskirche, Johann Sebastian Bach started work on a major collection of keyboard works under the collective name of ‘Clavier-Übung’. This collection was already published in several instalments during the 18th century, and it would ultimately grow into a standard work for every keyboard player, one which contains the essence of Bach's keyboard artistry. In the extensive third section of the Clavier-Übung, the organ is of central importance. In addition to an imposing prelude and fugue, Bach composed 21 so- called chorale preludes for organ for this collection. Every one of them is a masterpiece, in which Bach makes use of complex polyphony, invertible counterpoint, and canonic techniques. Bach also employs a very wide range of musical styles. The chorales which Bach used were common musical property in his day, recognizable, so to speak, for any listener. Today, since this is no longer the case, the Netherlands Bach Foundation is of the opinion that it is advisable to make them available as an addition to a complete recording of the so called ‘organ mass’. The choir of the Netherlands Bach Society, conducted by Jos van Veldhoven, performs the chorales in harmonizations composed by Bach himself, but also by his predecessors including Praetorius, Hassler, Schein, and Scheidt.