The Orgelbüchlein (Little Organ Book) BWV 599−644 is a set of 46 chorale preludes for organ – one of them is given in two versions – by Johann Sebastian Bach. All but three were written between 1708 and 1717 when Bach served as organist to the ducal court in Weimar; the remainder and a short two-bar fragment came no earlier than 1726, after the composer’s appointment as cantor at the Thomasschule in Leipzig. Bach's apparent plan was for a collection of 164 settings of chorale tunes sung during the Church year so that each part of the year was represented. However, only 46 of these were completed. The manuscript, which is now in the Staatsbibliothek, leaves a number of tunes as missing or "ghost" pieces. A project to complete the missing chorales called "The Orgelbüchlein Project" has been launched in the 21st century, where the chorales are written in modern styles. This project took nine hours in the first complete performance, giving an idea of the potential scope of Bach's "little" book. The Orgelbüchlein as Bach left it contains about 80 minutes of music which span the liturgical calendar. Each setting takes a Lutheran chorale, adds a motivic accompaniment, and quite freely explores form. Many of the preludes are short and use four contrapuntal voices. All have a pedal part, some requiring only a single keyboard and pedal, with an unadorned cantus firmus. Others involve two keyboards and pedal. These include several canons, four ornamental four-part preludes with elaborately decorated chorale lines, and one prelude in trio sonata form. A further step towards perfecting this form was taken by Bach when he made the contrapuntal elements in his music a means of reflecting certain emotional aspects of the words. Pachelbel had not attempted this; he lacked the fervid feeling which would have enabled him thus to enter into his subject. And it is entering into it, and not a mere depicting of it. For, once more be it said, in every vital movement of the world external to us we behold the image of a movement within us; and every such image must react upon us to produce the corresponding emotion in that inner world of feeling. Here Bach has realised the ideal of the chorale prelude. The method is the most simple imaginable and at the same time the most perfect. Nowhere is the Dürer-like character of his musical style so evident as in these small chorale preludes. Simply by the precision and the characteristic quality of each line of the contrapuntal motive he expresses all that has to be said, and so makes clear the relation of the music to the text whose title it bears.