Adagio cantabile — harmonic and formal analysis

A♭ major governs all 73 measures without modulation. The movement is a rondo: three statements of the main theme alternate with two episodes, and close with a coda. Each episode pursues the chromatic tension the theme withholds — before the varied return absorbs that chromaticism as a native element of the theme itself.

Every harmonic reading is derived from the score at the beat level. The analysis covers Roman numeral identification, cadence inventory, voice-leading observation, and the movement's structural argument — including how the theme's rotational harmonic cycle, the C major intrusion of Episode 1, and the modal shift of Episode 2 each relate to the single tonal centre that never wavers.

A rotational harmonic cycle that returns to where it began

The theme opens in root-position A♭ major with a harmonic cycle — I–V⁶–I–V⁶–vi–II⁷–V — that circles back to its starting point rather than driving toward a goal. The vi chord and chromatic predominant II⁷ at m. 316 introduce the flat side of the key; an ascending chromatic figure in the melody at m. 317 b.2.5 marks the dominant arrival. This chromatic fingerprint recurs in every subsequent statement of the theme.

The intensified restatement (mm. 322–329) repeats the same harmonic cycle in thicker texture — four notes expanded to six — and closes with the movement's only PAC at m. 329 b.2: root-position V⁷ to root-position I, bass and soprano both on scale degree 1. This is the movement's single moment of unambiguous cadential arrival.

C major introduced — as colour, then structural event, then dissolution

Episode 1 introduces E♮ — a pitch lying outside A♭ major — as its governing idea. The opening subgroup (mm. 329–335) alternates C major with diatonic harmonies, the chromatic semitone heard first as colour before building to a density peak at m. 335. The texture then collapses abruptly to a bare dominant at m. 336.

The episode closes without a cadence. A stepwise chromatic descent in the middle register across mm. 339–341 converges on an open dominant pedal, the texture reduced to near nothing. The chromatic tension accumulated since m. 329 is not resolved — it is suspended, waiting for the truncated return to absorb it.

A return defined entirely by what it omits

The truncated return reproduces the theme's opening phrase with near-literal fidelity — mm. 343–348 identical to mm. 315–320, the rotational harmonic cycle and chromatic fingerprint both unchanged. The same vi chord, the same II⁷, the same chromatic ascent at the dominant arrival.

What is missing is the intensified restatement. Where the first statement continued with a thicker texture and drove to a PAC, the truncated return closes at m. 349 b.2 with a weak IAC — soprano on scale degree 5, not scale degree 1. The structural truncation is marked entirely by what does not happen: no second arch, no PAC, no cadential weight.

Modal shift, chromatic-third motion, common-tone thread

Episode 2 shifts directly from A♭ major to A♭ minor at m. 349 b.2.5 — a change of mode, not of key. An ostinato figure establishes the minor tonic, C♭ saturating the soprano. The harmony then moves to ♭III and ♭VI in a chromatic-third excursion, a sustained B♮ threading all three harmonies as a common tone — the episode's most distinctive voice-leading feature.

The return to A♭ major is managed by a diminished-seventh bridge at mm. 361–362, resolving to V⁷ at m. 363 b.2.5. As in Episode 1, the close is not a cadence — the episode dissolves into the dominant preparation that launches the varied return, tension passed forward rather than resolved.

The surface transformed — the expected cadence withheld

The varied return restores A♭ major and the full two-part arch of the theme, but the surface has been transformed: inner-voice figuration is richer and chromatic passing tones are absorbed as native elements rather than episodic intrusions. The harmonic cycle runs unchanged; the textural climax falls at mm. 372–374.

The cadential approach at mm. 376–378 parallels the first statement exactly — but the expected PAC does not arrive. The dominant seventh lands on a weak beat, the inner ostinato continues without caesura, and the harmony moves directly to an unstable tonic. The tension is passed unresolved to the coda, the evaded cadence making its arrival necessary.

Settled by plagal motion and descent — not by cadence

The coda opens over a residual dominant pedal, the truncated chromatic figure completing its motion at m. 380. The harmonic motion from there is a IV–I plagal alternation through mm. 380–383 — confirmatory rather than argumentative, the movement's only extended plagal passage. The sole dynamic marking of the movement, mf at m. 383 b.2, falls within this withdrawal.

From m. 384 the melody descends by successive thirds — to C at m. 384, to A♭ at m. 385, an octave lower to A♭ at m. 386 — the texture thinning to bare tonic. The movement ends through registral and textural withdrawal, not harmonic resolution. The evaded cadence of m. 378 is never answered; it is gradually left behind.