"The pedals are an essential part of the organ: by them alone is it exalted above all other instruments, for its magnificence, grandeur, and majesty depend upon them.... The great organ, provided with pedals, must be so managed that its whole compass is brought into action; in others words, the composer and the player must require from it all that it can perform. Nobody has ever done this more than Johann Sebastian Bach."²

Johann Nikolaus Forkel wrote the above statement in his Bach Biographie of 1802 followed by a list of what he opined were the best organ compositions of Bach:

"1) Grand Preludes and Fugues, with obbligato pedal,
2) Preludes on the Melodies of several Chorales... (with obbligato pedal), and
3) Six Sonatas, or Trios, for two claviers and obbligato pedals. Bach composed them for his oldest son, Wilhelm Friedemann, who, by practicing them, had to prepare himself to become the great performer on the organ that he afterward was. It is impossible to say enough of their beauty. They were composed when the author was in his most mature age and may be considered as his chief work of this description. "²

Wilhelm Friedemann was approximately 13 years old around 1727, when Bach finished the trio sonatas in Leipzig. Ever resourceful, Bach used the second movement of Trio #3 (BWV 527) as a concerto for harpsichord, flute and violin, BWV 1044. He also recycled the first movement of the fourth sonata (BWV 528) as the second part of the cantata, Die Himmel erzählen die Ehre Gottes, BWV 76/8 in a trio sonata movement for oboe d'amore, viola da gamba and continuo.³ The third movement of the fourth sonata was originally placed between the Prelude and Fugue in G-major, BWV 541. The second movement of the fifth sonata first appeared as a middle movement in an early version of the Prelude and Fugue in C Major, BWV 545.⁴

Two Berlin manuscripts of the trio sonatas exist, namely P 271 and P 272. P 271 is credited to Johann Sebastian Bach, and was in the collection of Carl Philipp Emanuel. Wilhelm Friedemann owned P 272, which contains both his handwriting and Anna Magdalena's. In comparison to P 271, P 272 reveals many note and ornamentation discrepancies. P 271 includes the tempo indications that are absent in P 272. The manuscripts of the Leipzig chorales and the canonic variations on Vom Himmel hoch are also found in P 271.⁵

The complete sonatas as well as parts of the collection were transmitted in various copies throughout the 18th and 19th centuries. The trio sonatas have also been arranged for two harpsichords and for string trio.⁶ The three earliest published versions of the six trio sonatas appeared by Wesley and Horn in London, 1809-10 as a three-hand pianoforte work; by Nägeli as an Orgelschule in 1827; and in the first Peters edition, edited by Forkel's student, Friedrich Konrad Griepenkerl, in Braunschweig in September, 1844.⁷

Bach's oft-used heading, "à 2 Clav. ed Pedal," generated speculation that the trio sonatas may have been written for a double-manual pedal clavichord, harpsichord, and/or organ. In his book on Bach in 1908, Albert Schweitzer discussed the various instruments Bach used, including the organ, clavichord, and clavicembalo. He states:

"In order to get at least two degrees of tone, in Bach's time clavicembali were built with two keyboards, one manual being for forte, the other for piano; further improvements were a pedalboard, also provided with strings, and a manual coupler by means of which the lower manual could be made to sound simultaneously a higher octave. It was for clavicembali of this kind that the Goldberg Variations, the Italian Concerto, and the so-called organ sonatas of Bach were written."⁸

Although Schweitzer appears to assert that the trio sonatas were written for harpsichord, he continues by stating, "Speaking generally, all organ works could be played on these instruments,"⁹ in keeping with one common assertion that the use of keyboard instruments was relatively interchangeable in Bach's time.

For the majority of the trio sonata movements, Bach used a fugal structure in the upper two voices with tonic-dominant entrances accompanied by a continuo-like obbligato bass in the pedals. However, BWV 526,i, BWV 527,ii, and BWV 529, i each opens with an accompanied duet in parallel thirds, and BWV 530,i begins with both upper parts in unison. Ritornello and da Capo designs permeate the movements and diverse themes, keys, and meters are employed throughout. The consummate musical ecologist, Bach reveals an Italian influence including borrowed concerti ideas in his trio sonatas.

A letter written in 1788, possibly by Carl Philipp Emanuel Bach, included the following summary about the trio sonatas:

"In addition to the chorale settings and variations J.S. wrote, and the preludes to them, various trios for the organ have become known, particularly six for two manuals and pedal that are written in such galant style that they still sound very good, and never grow old, but on the contrary will outlive all revolutions of fashion in music. All in all, no one has written so much beautiful music for the organ as J.S. Bach."¹⁰

¹The New Bach Reader (NBR), ed. by Hans T. David and Arthur Mendel, rev. and enlgd. by Christoph Wolff, NY: W. W. Norton & Co., 1998, 470.
²NBR, 471-2.
³Christoph Wolff et. al., The New Grove Bach Family, NY: W. W. Norton & Co., 1983.
⁴Oxford Composer Companions. J.S. Bach, ed. Malcolm Boyd, Oxford University Press, 1999: John Butt, "Organ Sonatas," 347-8.
⁵Johann Sebastian Bach. Neue Ausgabe Sämtlicher Werker (NBA). Ser. IV, Band 7, critical commentary by Dietrich Kilian. Kassel: Bärenreiter, 1988, 13.
⁶NBA, 59.
⁷NBA, 62.
⁸Albert Schweitzer, J.S.Bach, Eng. tr. by Ernest Newman, NY: Dover, Vol. I, 1966, 201.
⁹Ibid.
¹⁰NBR, 406.