It should come as no surprise that nearly half of all of Bach's organ music is based on the German Lutheran chorale. Bach's companionship with the Lutheran hymnal began early, and throughout his life it served as a source of inspiration and stimulation. This affection for the chorale was not merely personal, but was rather an integral part of his nation, as much a prop of their faith as was the Bible itself. Furthermore, the very structure of the Lutheran church service provided the organist numerous opportunities to improvise on chorale melodies, specifically, while introducing a hymn, alternating stanzas with the choir and congregation, and during the service of holy communion.

Among all of Bach's chorale-based organ music, the Leipzig Chorales allow us a unique glimpse into the mind behind the music. Virtually all of the Leipzig Chorales are re-workings of earlier pieces composed during Bach's Weimar period (c. 1708-1717). That Bach returned to these pieces near the end of his life may be evidence of his wishes to prepare the collection for publication. Unlike the Orgelbüchlein and Clavierübung III, there is no apparent liturgical organization to the Leipzig Chorales. Rather, Bach's purpose in this collection is that of paying tribute to the late seventeenth-century German masters--Johann Pachelbel, Dieterich Buxtehude, and Georg Böhm, in particular--who demonstrated the various ways of setting a chorale melody.

It is unfortunate that nineteenth-century scholars have mistakenly assumed the Leipzig Chorales comprise eighteen pieces, thus the formerly assigned titles Eighteen Chorales and Eighteen Great Chorales. Unfortunately, Bach left no title or table of contents for this collection. A single-bound manuscript (P.271) in the German Staatsbibliothek contains the six Trio Sonatas followed by the first fifteen Leipzig Chorales in Bach's autograph, the next two Leipzig Chorales copied by Bach's son-in-law, the Canonic Variations on "Vom Himmel hoch" in Bach's own hand, followed by a fragmented chorale, "Wenn wir in höchsten Nöten sein" (here titled "Vor deinen Thron tret ich") copied by an unknown scribe. Recent scholarship has suggested that "Vor deinen Thron" was not at all included in Bach's plan for the Leipzig collection and has also refuted the long-believed romantic notion that Bach, on his deathbed, dictated note-by-note to his son-in-law his final swansong. Furthermore, that the Neue-Bach-Ausgabe edition of the Bach works titles the collection Seventeen Chorales and because the collection is framed by large plenum pieces evoking the Holy Spirit provides strong evidence that the collection comprises seventeen chorale preludes.

Throughout the Leipzig collection, we view Bach drawing from the rich musical traditions of both North and South Germany as well as Italy. These influences can be clearly seen in the many different ways of setting a chorale melody for an organ with two manuals and pedal, initiated early in the seventeenth century by Jan Pieterszoon Sweelinck in Amsterdam and later formulated by Samuel Scheidt in his Tabulatura Nova. The Leipzig collection includes examples of the following types of chorale preludes:

Paraphrase Chorale in which the accompanimental figures are derived from the chorale melody: BWV 651, BWV 655, BWV 656, BWV 657, BWV 664, and BWV 665

Ornamented Chorale in which the cantus firmus is decorated: BWV 652, BWV 653, BWV 654, BWV 659, BWV 662, and BWV 663

Trio Chorale in which three voices are treated independently: BWV 655, BWV 660 (two lower voices in canon), and BWV 664

Manualiter Chorale: BWV 656 (variations one and two), and BWV 666 (excepting a two and one-half measure pedal-point)

Organo pleno Chorale or Cantus Firmus Chorale in which the melody is assigned to the pedal voice: BWV 651 (Organo pleno), BWV 658, BWV 661 (Organo pleno), BWV 665 (Organo pleno), and BWV 667 (Organo pleno)

Variation Chorale: BWV 656

Because all of the early versions are extant--most being found in manuscript copies by J. G. Walther and J. T. Krebs--it is enlightening to study the revisions Bach made in his later versions. The nature of the revision includes changes in figuration, ornamentation, note values, and rhythmic values. Some of the chorales received added length, either by a few or several measures. In some cases, Bach even corrected counterpoint errors such as parallel octaves or fifths! By comparing Bach's original settings of these chorale preludes composed early in his career with the same settings he revised near the end of his life, we are afforded a unique glimpse into the thought process of the genius at work, revealing both youthful creativity and mature mastery.