Bach did not use this episodeless structure in quite such concentrated form again, though there is something of it in the D major, E major, and B flat minor fugues of Book II. For Marpurg this type of fugue, which he called strict fugue or fuga obligata, was specially characteristic of Bach, though he was probably thinking here of The Art of Fugue. But for most of the 48 Bach in fact turned decisively to a type of free fugue (fuga libera) which Marpurg associates more with Handel. In it the principal subject is not always present, and there are well-devised modulating episodes related thematically to the subject or countersubjects (1753 pp.19–20; NBR p.353). Bach’s main concern in reworking Reinken’s fugues was the addition of just such episodes, and the extension of tonal range: Reinken may have been the composer he criticised in conversation with Marpurg for not having ‘enough fire to reanimate the theme by interludes’ (‘das Thema durch Zwischenspiele aufs neue zu beleben’, Dok.III p.145, NBR p.363; C. Wolff 1991 pp.69–70).
This loosening of structure and separation of the incidences of the main material derives principally from Bach’s use of the Vivaldian ritornello principle which he began to explore systematically from around 1713, though he had been well aware of it before then.33 The amalgamation of formal and stylistic prototypes always held a fascination for Bach, and at Weimar he explored in vocal works various ways of integrating the orchestral sinfonia into the choral fugue (W. Neumann 1938 p.54). The combination of fugue and concerto is in its most classically condensed form in the C minor fugue of Book I, where blocks of triple counterpoint are separated by thematically derived episodes. A more expansive version of this combination, with broader concertante figurations, is in the G major fugue of Book I. At Cöthen Bach used in various works a combination of fugue and concerto ritornello with reprise, as in most of the preludes to the English Suites and several fugal allegros in the sonatas for obbligato harpsichord and violin. This is also the scheme used in the C sharp major fugue of Book I. In fact Bach had a number of favourite formal procedures which he could adapt to fugal materials as well as to any other ones.
The ritornello principle as used by Vivaldi in his Op.3 concertos was a very
flexible and fruitful one. Some Allegros have non-thematic solo breaks based on harmonic figurations, such as that in Op.3 No.2, a charming movement which fades out unpredictably in a way that fully justifies the title ‘Harmonic Caprice’ (L’estro armonico). This type of relationship of episode to exposition is in the F sharp major fugue of Book I, in which the derivation of episode figures from the exposition is not obvious. Other Vivaldi movements develop motifs fairly logically during the solo breaks, as in Op.3 No.8 (arranged for organ as BWV 593). This type, which does something with the material, is the one that most appealed to Bach, judging by the concertos he chose to arrange for keyboard. Even when the episode material seems radically different from the exposition and in a relaxed concertante harmonic pattern, as in the E minor organ fugue BWV 548/2, the argument of the piece amalgamates and integrates the two types of material. A standard procedure with Vivaldi is to have the main ritornello, then a short solo break, then a repetition of all or part of the ritornello, then a longer solo break which eventually modulates to a new key. This pattern may be seen fairly straightforwardly reproduced in some of Bach’s large concerto fugues such as the G minor fugue for organ BWV 542/2, which he may have played in Hamburg in 1720. In this the entire exposition is repeated in the tonic. In combining the concerto principle with the fugue, with the exposition corresponding to the tutti ritornello, Bach generally exploits the second tonic exposition in some way. In the G minor organ fugue the order of entries is adjusted so that the pedal entry is in the tonic the second time, in order to provide a suitable conclusion to this large opening tonic block. The equally concertante G major fugue of Book I uses the same pattern, but with the subject inverted in the second tonic exposition. Not many fugues of the 48 are on this expansive scale so the repetition normally amounts only to a single extra tonic entry after the end of the exposition (the E flat major and A flat major fugues of Book I).
The concerto principle may be used to aerate with episodes a fugue based on expositions such as the G major fugue of Book I, which in its main material follows a scheme of inversions and stretti comparable to the A minor fugue of Book I; or one based on blocks of invertible counterpoint (the C sharp major and C minor fugues of Book I). But the ritornello is more usually represented by only one or two entries of the subject. A condensation of the concerto idea that Bach likes to use as a basic model, though always with variety of detail, is to have an initial exposition, followed by an exposition in the sense that there is an entry in each voice, but in different keys and spaced out by thematically developmental interludes (the F sharp major, F sharp minor, and B major fugues of Book I). A similar procedure is used by Bach in arias, where the opening instrumental ritornello is re-run in expanded form when the voice enters. This allows Bach to make, as Marpurg says, ingenious transpositions of the principal subject into other keys and exploit a rich vein of subsidiary ideas
The Concerto principle 103
(Dok.III p.144, NBR p.363). It also has the no less important rhetorical function of ‘reanimating the theme’ by presenting it in different contexts and revealing all sorts of unsuspected aspects of it, so that finally even the most ordinary idea can, through accumulated experience, become utterly compelling. The Vivaldi experience helped Bach to consolidate, and dramatise, a tendency he had already developed in fugal writing. An important part of his interest in fugal structures was their dramatic potential, something relating to his own skill and spontaneity as a performer. In this Bach’s grasp of dispositio, of arranging his materials based on his sense of a listener’s expectations, is a crucial element of success.
‘. . . through all the tones and semitones both as regards the tertia major or Ut Re Mi and as concerns the tertia minor or Re Mi Fa.’
We are so accustomed to the equal-tempered chromatic scale as a fundamental musical material that it takes some effort to appreciate the novelty and sophis- tication of the system reflected in Bach’s terminology. The view that the tradi- tional modal system was an antiquarian anachronism and a primitive step on the way to the clear light of tonal day does not do justice to the rich period at the beginning of the eighteenth century when several traditions overlapped and enmeshed, giving rise to a complex system in which composers were sensi- tive to the possibilities of different materials and the tensions between them.1 Bach was in the forefront of the development of the tonal system, but he also regarded all current materials as useful and was prepared to use old ingredients when appropriate.
His primary work for demonstrating the full development of tonality is of course The Well-tempered Clavier, so that is not where we can most profitably look for modal ingredients.2The two essential elements of the tonal system are present in the title-page formulation: the possibility of using all 12 semitones as tonics, and of each scale having a major and minor form. But these are not expressed in what was even in 1722 the standard terminology. Later sources, copied when the fully developed tonal system had become a commonplace, expressed it in standard modern terms such as ‘through all the major and minor keys’ (‘durch alle Dur und Moll-Töne’).3Yet Bach avoided this simplicity in 1722, and none of these terms was unambiguous at that stage.
In their primary senses the terms tone and semitonia were purely geograph- ical in relation to the keyboard, rather than reflecting a theoretical concept of key. Taking the modern piano keyboard as the norm, tone are the white notes and semitonia the black notes; subsemitonia are split black notes. This is not the