J. S. BACH Jonathan Berkahn - Victoria University - Victoria ...

movement as a minuet writ large) 29 but the same tonal structure becomes something
quite different when expanded to sonata dimensions. This is a case where size really
does matter.
In a sense, the source of this change in significance is the very closeness of the
I-V relationship. Even if approached by way of its dominant, it is surprisingly difficult
to hear the dominant as a key in its own right—it always threatens to return to its
original role, and point the way back to the tonic. In order to establish the dominant
securely as a new tonic, an immense amount of reinforcement and overstatement is
required. A shift which occurred as a matter of course in small-scale forms is thus
dramatised when expanded to sonata proportions—this shift to the dominant is quite
simply the most important thing that happens during a sonata exposition, a process that
makes sense of every other event.
While this same modulation usually does occur in a fugal exposition—several
times, perhaps—the essential mechanism of a fugal exposition has nothing to do with
modulation at all. Instead, it is all about opening up registral space, defining the mode
by successively exposing tonic and dominant pitches (not keys). This is why tonic
must be answered with dominant, dominant with tonic, and therefore the reason for the
arcane mysteries of the tonal answer. 30 Once this is understood, everything else falls
into place—tonality is an entirely secondary consideration. It is quite possible to have
a fugal exposition with virtually no modulation at all (Ex.0.1).
To be sure, many expositions do fall into the standard nineteenth-century
‘subject in tonic: answer in dominant’ pattern (Ex.0.2), especially where the subject is
lengthy or harmonically oriented; but in general it is unwise to assume that the key of
29 Versuch einer Anleitung zur Composition (Leipzig, 1782-93), tr. N. K. Baker as Introductory essay
on composition: The mechanical rules of melody, Sections 3 and 4 (New Haven: Yale University
Press, 1983), p.118 (Pt III: 39).
30 The clearest exposition of this question I have yet found is in Roger Bullivant’s book Fugue
(London: Hutchinson, 1971), pp.56-74, which includes a truly virtuosic analysis of the answer to
Buxtehude’s ‘Gigue’ Fugue, BuxWV 174. See also P. Walker, ‘Modality, tonality, and theories of
fugal answer in the late Renaissance and Baroque’, Church, stage, and studio: music and its
contexts in seventeenth-century Germany (Ann Arbor: UMI, 1990), pp.361-388.
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