Bach produced a wealth of pedagogical materials, both in content and quantity, including The Well-Tempered Clavier, Inventions, and Sinfonias. These were developed from the outset with clear and meticulous planning, often involving selections from various candidates to suit specific purposes, as well as transpositions and revisions. On the other hand, numerous works remained that were not incorporated into collections, along with pieces presumed to be original versions in different keys, and simplified early drafts. The Nine, Six, and Five Little Preludes were likely compiled by later generations from such small pieces, and were similarly transmitted from pupil to pupil as pedagogical material. The compilation method for these collections appears to have been established and popularized by the Peters Edition's keyboard works (edited by Czerny/Griepenkerl) in the mid-19th century.

All of these Nine Little Preludes originate from The Clavierbüchlein for Wilhelm Friedemann Bach. They were formerly published and widely known as "Twelve Little Preludes," comprising the six pieces from BWV 925-930, the Five Little Preludes, and the Prelude in C minor, BWV 999. Currently, it is customary to group eight "Preludes (Praeludium or Praeambulum)" that were not selected for systematic collections, along with a Minuet added by Bach to a Stölzel Partita, to form a set of nine pieces. It should be noted that in The Clavierbüchlein, these pieces are arranged in the order of 924, 926, 927, 930, 928, 924a, 925, 932, 931, 929, which does not align with the BWV numbering sequence—nor with their probable composition dates. However, for convenience, this section will discuss them in BWV numerical order.

1. C major, BWV 924

The first half features arpeggiated chords played by both hands, while the second half consists of an organ point and passage work. This structure is reminiscent of the Prelude No. 1 from The Well-Tempered Clavier, Book I. While the harmonies are much simpler, the chords in the left hand are embellished with ornaments, creating momentary variations. The ranges of both hands do not even approach each other, let alone cross, with the harmonic tones of the right hand floating above the deep resonance of the left.

2. D major, BWV 925

The theme appears alternately in both hand parts. Based on the handwriting, it is suggested that this piece might be by W. F. Bach. Furthermore, its scrupulous imitation and somewhat awkward thematic development seem to support this theory, though it is undoubtedly written under the supervision of J. S. Bach.

3. D minor, BWV 926

The opening begins ambiguously, without clearly establishing whether it is in 3/4 or 6/8 time. Quarter notes then enter, but the eighth-note motive continues to progress ambiguously. The hemiola that appears after passage work spanning the full width of the keyboard provides a long-awaited cadence for the entire piece.

4. F major, BWV 927

The same figuration is repeated almost consistently, with a slight change in texture in the middle, at measures 8-9. The final three measures also prepare the cadence by varying the density of sound through monophony, chords, and rests.

5. F major, BWV 928

The entire piece is constructed using a rich variety of combinations of the opening theme, counter-theme, and thematic motivic material. Its development is so skillful that it could well be called an invention, but due to the less strict voice leading, it remains within the category of a prelude. The piece is symmetrical, with complete presentations and developments of the theme, concluding with perfect authentic cadences, placed at the beginning (measures 1-5) and the end (measures 20-24). The middle section, which passes through various keys via sequential progression, forms the musical climax of this piece. Roughly analyzed, it modulates to A minor in measure 10, and a perfect authentic cadence in A minor is presented in measure 17, indicating that it remains within the realm of A minor during this interval. However, the dramatic flow from measure 11, where it cascades into sequential progression in the lower voices, then abruptly rises rapidly from the latter half of measure 12 to regain stability, is quite dramatic.

6. G minor, BWV 929

This work is not a prelude but was inserted into Stölzel's Partita as a "Minuet Trio by J. S. Bach." Therefore, it should be performed not as a standalone piece, but rather as part of the entire suite, or at least together with Stölzel's Minuet proper. The Minuet proper sometimes feels too thin in texture due to the prevalence of half notes in the left hand and the quarter-note cadences played by both hands. In contrast, Bach's Trio consistently features flowing eighth-note motives and maintains a rich, three-voice texture throughout. Furthermore, while the Minuet proper primarily uses arpeggiated chords and turns as motives, Bach strategically employs stepwise motives with appoggiaturas. As a result, non-harmonic tones act like a spice, preventing monotony. This trio was also used in a transposed version in an early draft of the French Suite No. 3 in B minor (BWV 814a). The reason why Bach ultimately did not adopt this trio is currently unknown.

7. G minor, BWV 930

This is a rare work with fingering indications provided for almost every note. While it sometimes includes fingerings that may not be suitable for modern pianos or comfortable for a player's hand, faithfully adhering to these indications clearly reveals phrase breaks and accent placements. It is a valuable document that technically conveys the sound Bach intended. The piece is divided into two sections, with the second half beginning with an inversion of the opening of the first half. The cadences concluding each section are also of the same type, constructed to gradually increase in density using pedal points and ties. Such symmetry is a form often used in suite movements.

8. A minor, BWV 931

This is a short piece, about eight measures long, written by W. F. Bach. It features various ornamentation signs, many of which are French-style symbols not found in Bach's table of ornaments presented at the beginning of The Clavierbüchlein. Furthermore, some of these appear to be errors. It is possible that Friedemann practiced ornamentation by referring to some works or treatises other than his father's. In any case, it is unlikely that all eight measures are by Bach; perhaps his father provided only the bass line or framework, and Friedemann completed it.

9. E minor, BWV 932

Unfinished. Friedemann seems to have begun copying a work by J. S. Bach but interrupted the transcription for some reason. The opening begins with a three-voice fugue, and if completed, it would likely have been a considerably large-scale work.