Organ Sonatas (Bach)

The organ sonatas, BWV 525–530 by Johann Sebastian Bach are a collection of six sonatas in trio sonata form. Each sonata has three movements, with three independent parts in the two manuals and obbligato pedal. The collection is generally regarded as one of Bach's masterpieces for organ. The sonatas are also considered to be amongst his most difficult compositions for the instrument.
The collection was assembled in Leipzig in the late 1720s and contained reworkings of prior compositions by Bach from earlier cantatas, organ works, and chamber music as well as some newly composed movements. The sixth sonata, BWV 530, is the only one for which all three movements were specially composed for the collection.
When played on an organ, the second manual part is often played an octave lower on the keyboard with appropriate registration. Commentators have suggested that the collection might partly have been intended for private study to perfect organ technique, some pointing out that its compass allows it to be played on a pedal clavichord.

Origins and purpose

Instructional manual

The organ sonatas were first gathered together in Leipzig in an autograph manuscript which Bach scholars have dated to a period roughly between 1727 and 1730. Apart from the heading with the numbering of the six sonatas and an indication of where the manuscript ends, Bach himself left no further specifications. After Bach's death, the musician Georg Poelchau produced a covering page for the collection with a title and commentary.
The sonatas were described by Bach's biographer Johann Nikolaus Forkel as follows:
Poelchau's commentary on the covering page is a direct quotation of this passage from Forkel.
File:Sophienkirche-Dresden-Silbermann-Organ.jpg|thumb|left|Silbermann Organ in the Sophienkirche, where Wilhelm Friedemann Bach became organist in 1733
The organ sonatas represent the culmination of Bach's collections of keyboard works with a partly didactic purpose, from the point of both playing and composition. Although intended initially for Bach's eldest son Wilhelm Friedemann Bach, they also became part of the staple repertoire of his students. The keyboard collections include the Orgelbüchlein, the two and three part inventions, the first book of The Well-Tempered Clavier, the French Suites, and the Six Partitas.
Two main sources are known for the collection of sonatas. The first autograph score—possibly not the original composing score—is on paper with a watermark that allows it to be dated to the period 1727–1730. The second "fair copy" was started by Wilhelm Friedemann and completed by Bach's second wife Anna Magdalena. In addition, there are numerous other later copies by the circle of Bach, including copies of the first movement of BWV 527 and the slow movement of BWV 529 made by Bach's former pupil from Weimar, Johann Caspar Vogler. From these surviving manuscripts of the collection and the circumstances surrounding its composition—including Wilhelm Friedemann's future career and Bach's renewed interest in the obbligato organ in his third cycle of cantatas—the date when the collection was compiled can be roughly set at a time between 1727 and 1730, although without any precision.

Genesis of collection

From the two main sources, from Bach's knowledge of works by other composers and from his own compositions for organ and instrumental ensemble that predate the collection, it is possible to gain a partial idea of how the collection was put together and how the genre of the Bach organ trio evolved.
Some of the movements had precursors either as organ works or chamber works: only the last sonata BWV 530 had all its movements newly composed. The only other movements that are known with certainty to have been newly composed are the slow movement of BWV 525 and the first movement of BWV 529; the last movement of BWV 529 probably also falls into this category but might be a transcription of a lost instrumental trio sonata from Bach's periods in Cöthen and Weimar. Although Hans Eppstein has suggested that several movements might be transcriptions of lost chamber works, the writing for organ is often so idiosyncratic that his hypothesis can apply to at most a few movements.
There are six movements known with reasonable certainty to date from earlier compositions.
Four movements have previous versions as organ compositions:

the first movement of BWV 525;
the first movement of BWV 527;
the slow movement of BWV 528;
the slow movement of BWV 529.

Two movements are known to be transcriptions of instrumental trios:

The slow movement of the BWV 527 is a reworking of a lost instrumental work which was also re-used later in the slow movement of the triple concerto for flute, violin and harpsichord, BWV 1044. This arrangement has been ascribed to the period 1729–1740 when Bach was director of the Collegium Musicum in Leipzig, an association of town musicians that mounted concerts in the Café Zimmermann.
The first movement of BWV 528 is a transcription of the sinfonia that begins the second part of the cantata Die Himmel erzählen die Ehre Gottes, BWV 76, scored for oboe d'amore, viola da gamba and continuo., designated BWV 528a, is a reconstruction of an entire trio sonata for the same combination of instruments using the remaining two movements. The lost work is thought to date to Bach's period in Weimar. Pieter Dirksen's edition allows the performers a choice of three possible keys: G minor; E minor; or a mixture of the two.

Some individual movements were associated with other organ works of Bach: the earlier version of the slow movement of BWV 529—the most elaborate and skillfully written of the slow movements—was paired with the Prelude and Fugue in C major, BWV 545; and the last movement of BWV 528 was paired with the Prelude and Fugue in G major, BWV 541. It is now thought that these pairings originated in Bach's Leipzig period. One problem in deciding how the collection came about is that many instrumental works on which the organ sonatas might have been based have been lost. Such chamber works are mentioned by Carl Philipp Emanuel Bach in his 1754 Nekrolog and many are thought to have been composed in Cöthen. has suggested this might reflect the fact that, after Bach's death, his vocal works passed to Wilhelm Friedemann and Carl Philipp Emanuel who guaranteed their survival; while the chamber works, very few of which survive, were mostly inherited by Bach's younger sons Johann Christian Bach and Johann Christoph Friedrich Bach.
Corrections in the autograph manuscript and a detailed analysis of stylistic elements in the sonatas have led to suggest that the sonatas were composed in their final state in two distinct groups. The first group, consisting of the first, third and fourth sonatas, has first and last movements which have a fugal character and as close stylistic relation. The second group, consisting of the second, fifth and sixth sonatas where the bulk of composing corrections occur have a concerto-like form, with contrasting tutti and concertato sections in the opening movements and fugal final movements. Even in the second "fair copy" produced by Wilhelm Friedemann and Anna Magdalena, Bach made corrections in three movements.

Origins of organ trio

Although Bach created a unique compositional genre in this collection of sonatas, the roots of the organ trio can be traced back to the works of earlier composers and some of Bach's own earlier compositions for organ. Bach had in his possession many organ works by seventeenth century French organists such as Boyvin, Clérambault, Grigny, Lebègue and Raison who wrote trios, trios en dialogue and trios à trois claviers for two manuals and pedal, with distinctive registrations for each manual keyboard. Bach's sonatas however, with their binary or ritornello form, owe very little to these French organ trios.
Earlier models for Bach's type of organ trio occurred in the first versions of the trios in the Great Eighteen Chorale Preludes, particularly Allein Gott in der Höh' sei Ehr, BWV 664a, and Herr Jesu Christ, dich zu uns wend, BWV 655a. Both these chorale preludes were written towards the end of Bach's years in Weimar. Both BWV 664a and BWV 655a follow the pattern of the Italian trio sonata for two violins involving invertible counterpoint. In a more rudimentary form, trios of this kind already appeared in German organ music in a few of the freely composed chorale preludes of Buxtehude, van Noordt, Armsdorff, and Georg Böhm, Bach's teacher from Lüneburg. In the two chorale preludes of Bach, the organ trio became fully developed into a concerto-like fast movement: they are written in ritornello form, with the theme in the bass as well as the upper parts, which are written imitatively with virtuosic episodes. The first version of the slow movement of BWV 528 also dates from roughly the same period: instead of the larger scale structure of the two chorale preludes, the musical material is broken up into imitative two bar phrases, often of bewitching beauty. Although no longer having any liturgical references, the sonatas BWV 525–530 preserve the concerto-like quality of the two Weimar chorale preludes; like them the manual and pedal parts are written within an idiom particular to the organ rather than that of solo instruments like the violin or flute. On the other hand, there is very little similarity between the compositional style of the organ sonatas and that of Bach's organ transcriptions of instrumental concertos by Vivaldi and other composers.With their chamber music quality, the organ sonatas have clear affinities with Bach's sonatas for obbligato harpsichord and solo instrument—violin, viola da gamba and flute, also composed or compiled in Leipzig. They are all written in trio sonata form with binary and ritornello movements. Moreover, the collection of six sonatas for obbligato harpsichord and violin, BWV 1014–1019 seems to have involved a similar survey, recording all possible ways of writing for the instrumental combination. There are, however, significant differences:

the organ sonatas are conceived more in concerto form with three movements, whereas the instrumental sonatas have four or more movements like a sonata da chiesa;
the instrumental sonatas do not preserve a strict equality between the upper part—there is often a distinction between material for the melody instrument and the keyboard part, which can play a purely continuo-like role;
in the instrumental sonatas, either part can be divided, with the addition of an extra voice or double stopping;
while movements from the instrumental sonatas can be diffuse and expansive—possibly because more musical textures are available—movements in the organ sonatas are in general less concerned with texture, clearer in form, and more concise and succinct, sometimes to the extent of seeming like miniatures.

Probably the closest similarities between the instrumental sonatas and the organ sonatas occur in their fugal final movements in every aspect—texture, melody and structure. The distinction between sonata types was subsequently delineated by Scheibe, who introduced the term Sonate auf Concertenart to contrast with the sonata da chiesa, but there are as many exceptions to the rule as adherences. Commentators agree that the collection of organ sonatas marks one of the later stages in Bach's development of the trio form.
One of the main composers to develop the purely instrumental trio sonata was Bach's contemporary Georg Philipp Telemann, godfather to Carl Philipp Emanuel Bach and his predecessor as Kapellmeister in Hamburg. One of the only features that Telemann adopted from the older French tradition of the trio sonata was the adaptability of the instrumentation. Telemann's Six Concerts et Six Suites could be played on two or three instruments. Some movements in the Concerts occasionally show similarities in texture and form with Bach's organ sonatas: gives the following example from the second half of the second movement of Concert IV for flute and harpsichord in E minor, TWV 42:e3.
Some of the other movements of the Concerts have been cited by and as examples of the Sonate auf Concertenart. Later organ sonatas by Bach's student Johann Ludwig Krebs show a clear influence of Bach and closely imitate his style; conversely the newer galant style of writing, popular among Krebs' generation, can be discerned in some movements of BWV 525–530, for example the slow movement of the fourth sonata. Several organ trios written by Bach's students survive and are discussed in detail in and by Dirksen in.