Analysis by Key: Another Look at Modulation

CARL SCHACHTER
linear, contrapuntal structure. The tonicized C minor in the Bach Allemande is
indeed part of the return to I: as Ex. 9 shows, it moves within V from Bb to D,
and the D goes on to the tonic Eb . The return to I, then, is not from VI (C
minor), but from a prolonged V that encompasses the tonicization of VI. The
area governed by V changes its key focus several times: first from Bb major to C
minor, then through several tonicized chords (Ab major and F minor) that
belong both to C minor and to Eb ma jor, and before the final cadence, to Eb; the
core of these occurrences is a rising linear progression Bb (tonicized) - C
(tonicized)- D- Eb .
Because the key areas of the Allemande function within a contrapuntal web of
great (but typically Bachian) complexity, we cannot begin to understand them
without coming to terms with the voice-leading structure of the piece. In Ex. 9,
I have tried to illuminate the parts of this structure relevant to the subject of this
essay; I suggest that the graphs be read at first in the order presented, from
background to foreground. Much of the difficulty posed by the piece results
from the many transfers in register and from part to part (e.g. bass to soprano).
One structure disguised by such transfers is the rising fourth-progression from
Bb to Eb . Starting with level (b), the example shows that this large-scale linear
progression forms an enlargement of a motivic element fundamental to the
Allemande and indeed the entire Suite. The list of keys (eleven in ten bars of
music!) comes from the Grove article, whose author has underlined the
important, structural keys and has placed the transient ones in parentheses.
Note the curious place where a structural return to Eb is read; as in Tovey's
account of the E minor Prelude, this comes from analysing by key without
considering voice leading and chord prolongation.
Schenker's early writings about modulation also sometimes overlook linear
factors, but he does not make the mistake of equating all key successions with
chord progressions. In his Harmonielehre, he distinguishes among three
categories of chromatic elaboration: tonicization, where there is no sense of
departure from the tonic key; illusory keys (Scheintonarten), where the diatony,
or diatonic framework (Diatonie), recedes into the background but still exerts a
controlling influence; and true modulations, which do not return to their point
of origin, and which remain independent of any overarching diatony. 18
Schenker's illusory keys behave more or less as the Grove article indicates:
they can be regarded as expansions (and sometlmes as chromatic equivalents) of
diatonic scale steps. He cites the C major passage in the exposition of the first
movement of Beethoven's Piano Sonata, Op.7 (bs 81-9) and shows - very
convincingly, I think - that the V-I of C major represents an expanded and
chromatically elaborated VI-II progression in the locally governing key of Bb
maor.
Schenker's main example of real modulation is the development section of the
same movement, about which he says, 'the keys are real keys, and their
sequence is: C minor, Ab major, F minor, G minor, A minor, D minor. It would
be illicit to do violence to this situation by explaining all these keys or part of
them as consequences of the Bb major diatony which concluded the first part of
300 MUSIC ANALYSIS 6: 3, 1987