...for the profit and use of musical youth desirous of learning, and especially for the pastime of those already skilled in this study.
Many of the preludes of The Well Tempered Clavier are forerunners of the etudes of a later era, while the fugues are etudes of a specific kind themselves. No wonder that Chopin used Bach's music as a constant inspiration for composing as well as for warming up his hands (and mind) before playing the piano.
Prelude and Fugue No. 7 in E-flat major BWV 852 - The custom of pairing a prelude with a fugue began many years before Bach was active. The playing of an improvised prelude was twofold; to give the performer a chance to warm up his fingers and to set the home key of the fugue that was to come. Bach took this prelude playing tradition and enriched it. Prelude No. 7 of Book One is an excellent example of this, as it breaks the boundaries of tradition with a three-part form that includes a prelude, short fugue and a longer fugue. The first section is in true prelude fashion and runs for ten measures:
Th 3-voice fugue proper is based on a short, perky two-measure subject that begins, circles around and ends on B-flat, the dominant of E-flat major, but the chord outlined in the figuration is E-flat major.:
The next two measures has the subject revolve around the note E-flat, which is the dominant note of A-flat major, which is in actuality the chord that the figuration outlines. Most of the material in this fugue is in keys closely related to the home key of E-flat, including a short entry of the subject in C minor, the relative minor of the home key. The fugue ends with chromaticism and cadence.
Prelude In E-flat Minor, Fugue In D-sharp Minor No. 8 BWV 853 - Bach uses this prelude and fugue to show how the well-tempered keyboard can play in tune in keys containing many sharps or flats, something that was not possible with most other tunings. The prelude is in E-flat minor, a key that contains six flats:
The prelude begins with a bare E-flat minor triad. With rolled chords and modulations to B-flat minor and A-flat minor occur, and Bach's use of differing rhythms give this prelude a mood of reflection instead of sorrow. The mood brightens as the prelude ends in E-flat major.
The 3-voiced fugue is in D-sharp minor, a key with six sharps. The subject is about two and a half measures long, and it is truly the subject of this fugue as there is hardly much else going on besides the presentation and rehearing of the subject. Bach does create variety by varying the subject by inversion, augmentation and slight changes of rhythm.Prelude and Fugue No. 9 In E Major BWV 854 - The prelude is in a light polyphonic style and is short at only 24 measures:
The 3-voiced fugue has a terse subject of only a measure and a half in length:
Prelude and Fugue No. 10 In E Minor BWV 855 - This prelude is a reworking of a shorter prelude in the same key from The Notebook For Wilhelm Friedmann, a set of pieces for Bach's eldest son. It is in two parts, with the first part being an ornamented melody in the right hand accompanied by sixteenth notes in the left.
This continues until roughly at the half way point the tempo increases to presto and the right hand changes to running sixteenth notes along with the left hand:
Prelude No. 2 In C Minor of Book I. The prelude continues in this way until the ending cadence in E major.
A rare example of a 2-voiced fugue, it begins with a subject that consists of two bars of running, chromatic sixteenth notes and ends with two eighth notes:
Prelude and Fugue No. 11 In F Major BWV 856 - In the style of a two part invention, the opening parts for each hand reverse throughout this short prelude:
Prelude and Fugue No. 12 In F Minor BWV 857 - The musical interpretation of Bach's music can be a problem, or an opportunity, as one sees things. This prelude is a case in point:
The 4-voice fugue has subject of three measures: