Deciding Whether a Modulation Is Structural or Decorative
A student analyses the first 24 bars of a Classical sonata movement. Bars 1–8 establish the tonic, G major, with a clear perfect cadence in bar 8. Bars 9–16 introduce a new melodic idea over a repeated D major harmony, but the bass never cadences in D; instead a sequence in bar 14 pushes back to G, and bar 16 cadences again in G major. Bars 17–24 restate the opening melody with fuller texture, still in G. The student's draft essay calls bars 9–16 'the second subject, in the dominant,' and uses this to argue the movement follows sonata form. The teacher has flagged the claim as unsupported.
1. Evaluate whether bars 9–16 constitute a genuine modulation to the dominant. What evidence would settle the question?
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A modulation requires more than the presence of a new chord or a new melody. It requires the new key to be established by its own harmonic function, typically a cadence (often a perfect cadence with the dominant of the new key resolving to its tonic) and confirmation through the new tonic's own chords.
Here the evidence points against modulation. Bars 9–16 sit on repeated D major harmony, which is the dominant of G, not a new tonic. The bass never cadences in D: bar 14's sequence redirects back to G, and bar 16 cadences in G major. A key that never receives its own cadence and is abandoned before confirmation is not established. D major here functions as prolonged dominant harmony - a harmonic plateau - rather than a new tonic.
The student's claim therefore overstates the evidence. The passage may be a contrasting melodic idea over dominant harmony, which is a common device, but calling it 'the second subject in the dominant' asserts a structural modulation the music does not support. The evidence that would settle it is a cadence in D major, ideally a perfect cadence with A major (the dominant of D) resolving to D, followed by confirmation. Absent that, the analysis should describe the passage as dominant prolongation or a contrasting idea, not a modulation.
2. The student wants to keep the sonata-form argument. Explain what the student would need to show, and what a more accurate description of the passage would be.
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To keep the sonata-form argument, the student would need to demonstrate that bars 9–16 establish D major as a tonal centre. That means identifying a cadence in D - ideally a perfect cadence with A major resolving to D - and showing that D then functions as tonic, not as the dominant of G. The student would also need to show that the return to G in bar 16 is a later event, not a cancellation of the modulation. On the given evidence, none of this can be shown: the bass never cadences in D, bar 14 sequences back toward G, and bar 16 cadences in G. The modulation claim fails.
A more accurate description is that bars 9–16 present a contrasting melodic idea over a prolonged dominant (D major) that never achieves tonic status. The passage creates harmonic tension and contrast without changing key. This is still analytically interesting: it shows the composer building expectation of the dominant without confirming it, which sets up the return in bars 17–24.
The student can still discuss sonata-form features, but should do so carefully: the movement may exhibit sonata-like contrast and recapitulation without a full tonal migration to the dominant in this excerpt. The essay should distinguish between melodic contrast and tonal modulation, which are separate analytical questions.