The third of Schubert's second set of Impromptus is a set of sectional variations: an eighteen-measure theme, five variations, and a coda, each unit tonally closed and separated from the next by a cadence, a change of texture, or both. What the set holds constant is unusually large. What it varies is unusually free.
B♭ major governs the work, in a steady two-two Andante with a single tempo change late in the piece. Three structural key areas depart from the tonic and all three are related to it by third. Variation 3 turns to the parallel minor under five flats; Variation 4 moves to the flat submediant under six, the only unit to leave B♭ entirely; a two-bar retransition then carries the music home, standing under the six-flat signature while belonging tonally to what follows.
The two departures are connected. The key of Variation 4 is diatonic in the minor of Variation 3, and it is sounded there first as a passing chord within a descending-fifth chain — the excursion prepared a full variation before it is made. The chromatic vocabulary is otherwise consistent across all six units and rests on two recurring sonorities: a diminished seventh built on the raised fourth degree, which occupies the third bar of every consequent, and a chromatic mediant a third above the local tonic, which opens the second period of every unit. In the major-mode units that mediant needs an accidental foreign to the key and resolves at once as an applied dominant. In the minor variation it is diatonic and heads a sequence instead. The gesture is preserved and re-functioned.
The theme is a closed binary in two parallel periods, each a four-bar antecedent answered by a four-bar consequent, with a two-bar codetta appended. Both periods turn on the same dominant-arrival bar and both consequents begin from the same melodic pitch, so the design is exactly symmetrical before any variation touches it. The harmonic sequence is equally fixed: tonic, then a dominant seventh whose bass falls a fifth rather than rising to its root, then predominant and applied dominant into the half cadence that closes each antecedent. That falling approach governs every dominant arrival in the theme.
The two periods differ in what carries them to their closes. The first consequent substitutes the diminished seventh on the raised fourth degree where the antecedent had a diatonic predominant, and that substitution takes the period to its cadence. The second period opens on the chromatic mediant, holds submediant harmony, and then restores the cadential machinery note for note, so that the second half cadence is indistinguishable from the first. The codetta states the cadence twice more, the last time transposed down an exact octave in both voices — a device every codetta in the work will repeat.
The theme's registral design works in two directions at once. The melody traces two arches peaking on the same pitch, and both peaks fall on the diminished seventh, so the highest note is reserved for the theme's characteristic chromatic sonority. Beneath them the bass sinks steadily through each period. The dynamics align with neither: the theme's loudest marking falls where the formal restart and the chromatic mediant coincide, both registral peaks are quiet, and the codetta is quieter still. The loudest bar is not the highest, and the highest is not the most emphatic.
Variation 1 retains the theme's design without alteration and changes the number of voices. Two layers become four: the melody survives intact as a notated voice in longer values, continuous figuration runs beneath it, a structural bass holds the theme's own rhythm and pitches, and between them sits a syncopated inner line whose every onset falls off the beat. The variation does not dissolve the theme; it preserves it and surrounds it. That inner line thickens as each cadence approaches, and at the codetta it falls on the beat for the first time — the syncopation resolving precisely where the closing gesture begins.
The harmonic frame holds everywhere but one place, where a chromatic descent over a sustained pedal replaces the theme's route to the dominant. The destination is unchanged and the dominant arrives exactly where the theme placed it. Registrally this is the narrowest music in the piece: it abandons the theme's structural octave lift, restating its second phrase at pitch rather than an octave higher, and it is the quietest unit in the work, never rising above the theme's own opening level. The dynamic emphasis that had coincided with the theme's chromatic mediant is withdrawn at precisely the point where this variation introduces chromatic writing of its own.
Variation 2 keeps the frame more strictly still — no reharmonisation anywhere in its nineteen bars. What chromatic activity there is belongs to the melody: repeated appoggiaturas over unchanged harmony, and a rising line filling a fourth by semitone above a dominant seventh that does not move. The texture reverts to two layers, but the syncopation Variation 1 had confined to a single inner voice is transferred to the whole accompaniment, which strikes a bass note on the beat and a three-note chord four times off it. Where the previous variation had a syncopated line within a texture, this one has a syncopated texture. It restores the theme's octave transfer, then climbs past it, placing its ceiling — as the theme did — on the diminished seventh. It is the least adventurous unit harmonically and the most so registrally.
Variation 3 is the set's structural anomaly: the only variation in the minor, the only one to run three strains rather than two, the only one whose repeat is composed out rather than signed, and the only one whose second period genuinely reharmonises the theme. On the page it is a third longer than any of its siblings, but because its first strain carries no repeat barline it sounds the same length as every other unit in the set.
The written-out repeat is the first thing that needs explaining, since a repeat sign would have served had the music been wanted twice unchanged. Its melody is almost entirely literal at the octave; what differs is the accompaniment, which drops its bass doubling in three bars, so the music rises an octave and thins at the same time — the reverse of the intensification an octave lift usually carries. The real reason lies in the cadence. The first ending closes on a pitch the restatement lifts off from; the second closes on the pitches the following section will open with, handing the second period its own point of departure. The repeat was composed out because its ending had to do different work the second time.
Variation 4 is the tonal excursion, and it keeps the theme's harmony more faithfully than any variation that stays at home. What it transforms is register and disposition over a structure it leaves alone — and part of its colour is simply notational, since the key requires spellings the rest of the piece never needs. Its distinguishing feature is that the theme's melody begins in the bass, beneath its own accompaniment, the only such passage in the work. The two hands then exchange functions repeatedly, and each exchange lifts or drops the melodic line bodily, its rhythm retained exactly. What the theme accomplished by raising a phrase an octave is accomplished here by moving it to the other hand. The line sinks to the bass three times and rises further on each recovery, reaching the highest pitch in the piece.
The codetta is the only three-bar codetta in the set, and the extra bar exists to complete a three-octave descent in a single thinning voice. The bar that carries it also carries the hinge of the return: beneath a sustained tonic the melody rises to the one pitch that has been absent for twenty-two measures — the note that carries the theme's characteristic diminished seventh, reintroduced inside the foreign key one bar before the modulation becomes explicit. The retransition then makes it explicit and closes on nothing, withholding its resolution so that the boundary between the two variations is an elision rather than a cadence. It is the only such join in the piece, and it exists because Variation 4 is the only unit that has to find its way home.
Variation 5 inverts the method of Variation 1 exactly. Where that variation preserved the melody as a notated voice and surrounded it, this one dissolves it entirely into scalar motion, the theme surviving only as the accented pitches within the run. Beneath it the left hand reproduces not the theme's arpeggiated figure but Variation 2's blocked one — and this is the piece's quiet structural fact: the theme's own accompaniment occurs nowhere outside the theme, and never returns. The variation carries the highest ceiling and widest compass in the work, and its chromatic writing is confined to the scales themselves.
Its close is unique, and the alternative is written into the score. The first and second endings of the final consequent are identical but for their last few notes, differing in direction alone: one rises back into the repeat, the other descends out of it. The variation then restates its closing bar an exact octave lower before stopping altogether. A fermata stands over a rest in both hands — the only substantial silence in the work — and a second fermata holds a bare dominant octave already belonging to the new tempo. This is the only unit whose codetta reaches no cadence at all. Where Variation 4 needed a retransition to travel home, Variation 5, already home, is separated from what follows by a stop: two opposite solutions to the same problem of ending a variation.
The coda reverses everything the variations had built. The surface activity collapses in a single bar, the smallest note value lengthens threefold, and both hands move together in sustained block chords. It is a chorale, and it draws on the theme's second period rather than its first. The whole unit is then stated again an exact octave higher — every codetta in the piece has closed by octave descent, and the coda alone rises. Its only accents fall on its single chromatic chord, once in each statement, just as the theme placed its own dynamic peak on the chromatic mediant.
The last cadence is the point of the whole coda. Every cadence from the theme through the fifth variation arrives on the weak half of the bar. The perfect authentic cadence at m. 133 is the only one in the piece to fall on a downbeat. It is also the only one approached by leading tone rather than by the falling fifth that had governed every dominant arrival since the theme's second measure, and the only one whose tonic is struck by five voices at once and then sustained through a further whole bar. A metrically strong perfect cadence is withheld for a hundred and thirty-two measures and granted exactly once. The coda is not a sixth variation. It exists to supply the close that the theme and its five variations never provide.
| Section | Measures | Tonal area | What varies |
|---|---|---|---|
| Theme | mm. 1–18 | B♭ major | The referent. Two layers, melody over an arpeggiating left hand. |
| Variation 1 | mm. 19–37 | B♭ major | Voice count — two layers become four. Narrowest compass, quietest unit. |
| Variation 2 | mm. 38–56 | B♭ major | Register and dynamic level. The frame itself untouched. |
| Variation 3 | mm. 57–83 | B♭ minor | Mode, strain count, texture density. Written-out repeat. |
| Variation 4 | mm. 84–103 | G♭ major | Key, and the melody's assignment to the bass. Three-bar codetta. |
| Retransition | mm. 104–105 | G♭ signature, B♭ function | Nothing. It prepares the return, and closes on nothing. |
| Variation 5 | mm. 106–125 | B♭ major | The melody dissolved into figuration. Ends in silence, not cadence. |
| Coda | mm. 126–134 | B♭ major | Density, note value, and the metrical placement of the cadence. |
The cadential approach is restored note for note in both periods of the theme, so the two half cadences are indistinguishable — and every unit reproduces the pair.
Consequents close on the tonic in all but a single instance across the whole work, where an imperfect authentic cadence stands in its place.
Every cadence in the work up to the coda arrives on the second half of a two-two measure. Not one falls on a downbeat.
The only strong-beat cadence in the piece, and the only one approached by leading tone. Struck by five voices and sustained a further whole bar.
All forty-four cadences are mapped in the study guide with type, Roman numerals, and bass and soprano scale degrees.
The harmonic rhythm is fixed and the surface rhythm is not. Because the frame is retained in every variation, harmony changes at the same rate throughout the work — twice per bar through most of the design, four times in the cadential bars, once in each unit's opening bar of unbroken tonic arpeggiation. The surface meanwhile accelerates steadily from the theme through Variation 5, then collapses in the coda to below the theme's own level. That is the central textural fact of the piece: the harmony does the same thing seven times while the surface runs away from it and is then pulled back in a single bar.
The set's shape across its eight units is an arch with a dip at the start. Variation 1 is quieter than the theme it follows and contracts to the narrowest compass in the work while thickening its note count — accumulation and contraction at once. Variation 3 carries the highest note count in the piece yet the lowest onset activity of any variation, because its accumulation is vertical rather than rhythmic. It is also the only unit that slows the surface, and it does so at the midpoint. A variation set of this kind usually subdivides progressively faster; this one does not, and everything else that distinguishes the third variation points the same way.
There is no single peak. There are two, and they do not coincide. The dynamic peak falls in Variation 3, at the loudest marking in the work, followed one measure later by the quietest contrast in the piece. The textural and registral peak falls in Variation 5, where the densest measures, the widest compass and the highest ceiling occur together. Variation 4 sits between them, exceeding the third in register and the first in dynamic while leading in neither. Beneath both peaks the dynamic floor never moves: the quietest marking appears in every unit without exception.
Octave transfer organises the closes at every level — ascending within units at four separate points, descending at every codetta. The coda reverses it, restating its chorale an octave higher, the one upward cadential reiteration against five downward ones. In proportion the units are more equal than the page suggests: with the repeats observed, every unit from the theme through Variation 5 sounds the same length, and the single irregularity is Variation 4's extra measure, which exists to complete the descent into the return.
Analysis and study materials published as they appear.