Sonate Grande in G minor, Op. 39  Eberl's last sonata. Commissioned by Grand Duchess Maria Pavlovna of Saxe-Weimar-Eisenach during his concert tour to Weimar in 1806, the work was published shortly after his death by Thadé Weigl in Vienna, and later by Breitkopf & Härtel. As Christopher Hogwood, editor of the Edition HH publication, points out, its skillful construction is striking, featuring innovative forms and tonal plans, and a unification of the entire work through a common melodic sequence (a leap of a sixth and a descent of a second) across all movements. Furthermore, the expansion of the high register and the detailed dynamics surpass the limits of Eberl's previous sonatas, and the minute pedal indications are noted to represent a transitional state in pedal usage between the preceding generation (e.g., Mozart) and the subsequent one.

First Movement: Allegro appassionato 2/2 G minor

Exposition

Although the framework of sonata form is employed, the movement has a strong fantasia-like character due to the scarcity of regular phrase structures and tonally stable regions. Even the tonic region, which opens with a motto-like motive (a), lacks thematic completeness as it does not present periods consisting of equally long antecedent and consequent phrases, nor perfect cadences. Moreover, as early as measure 6, the opening motive is fragmented, and the key temporarily deviates from the tonic, thus blurring the thematic character of the opening idea. Furthermore, just as the first perfect cadence in G minor appears in measure 19, it immediately transitions into the beginning of an improvisatory transition section. Here, without harmonic breaks, new material is introduced one after another, while both hands traverse a wide range of the keyboard. The secondary theme begins not in the relative major, but in E-flat major, the submediant key, which is the same as the middle movement. The secondary theme, moreover, contrasts with the opening of the movement in that it possesses a periodic structure. Conversely, connections to the movement's opening material can be observed in the dotted-rhythm motive, stepwise motion, and secondary dominant chords of the consequent phrase. From measure 57 onwards, there is a modulatory, fantasia-like section, which is positioned as a transition to the closing section. Here too, phrases common to the transition to the secondary theme are discernible in terms of melody and texture, making it clear that the composer carefully used material to link various parts within the movement. In the closing section, motive (a) is persistently repeated, while the key continues to shift. As soon as this monotonous flow is interrupted by a chord progression containing the intense dissonance of an augmented sixth chord, the right hand rushes down from the high register over a diminished seventh chord, joining the left hand in octave unison, leading to the repetition of the exposition or the development section.

Development—Recapitulation

The development section can be divided into three parts based on material from the exposition. Furthermore, as if to balance the extensive use of the movement's opening motive (a) in the development, the recapitulation up to the secondary theme is omitted. That is, the passage over the G minor dominant at the end of the development section is directly followed by the passage from the exposition's transition, and without recapitulating the movement's opening, the secondary theme is recapitulated in G major, the parallel major of the tonic. The remainder of the movement largely follows the standard sonata form, with the exception of a shortened transition to the closing section and the G major beginning of the closing section. The movement concludes powerfully with a virtuosic passage and a fortissimo octave chord progression.

Second Movement: Adagio molto espressivo 4/4 E major

In ternary form. While section A is characterized by chord progressions in all voices in its first half and arpeggiated eighth-note accompaniment in its second half, the accompaniment patterns in A' and A'' change to shorter note values—sextuplet arpeggios and sixty-fourth note tremolos, respectively, much like in a variation form. Additionally, sections B and C share commonalities, thus also giving a variation-like impression. Section A (24 [12+12] measures) features arpeggios descending by thirds (motive a) and chorale-like chord progressions. Furthermore, both the first and second halves temporarily modulate to keys related by a third, which Eberl favored. In A' and A'', the section corresponding to measures 10-20 is omitted. Section B contrasts with section A through its monotonous chordal accompaniment. Harmonically, it is somewhat unusual that the subsequent A-flat major A' is prepared by the remote keys of D major and D minor. Moreover, A' is written in a bel canto style, with the melody ornamented like a virtuosic vocal part. Section C shares commonalities with section B in its left-hand chordal accompaniment and stepwise descending melody containing syncopation, while its tonality is, in contrast to section B, stable. In the coda, motive (a) is persistently repeated against a background of chordal tremolos. The end of the movement transforms into a recitative-like style, with both hands spinning out the melody in octaves, interspersed with fermatas. Here, motive (a) and the opening motive of the final movement appear alternately, and finally, the music rests on the supertonic of G minor, with the right hand descending by a second, seemingly sliding into the beginning of the final movement.

Third Movement: Allegro agitato vivace assai 3/4 G minor

In sonata form. This is a pathos-filled movement, rich in fluctuations of tempo and dynamics. The similarity of the thematic motives to the final movements of two Beethoven sonatas composed before this work, Op. 14 No. 2 (1798) and the 'Tempest' Sonata (1802), has been repeatedly pointed out in scholarly history. The transition section presents an interesting correspondence between the beginning and end of its sections. Specifically, the beginning of the modulation starts with an ascending scale in the bass, and a descending scale leads to the beginning of the secondary theme group (long-valued left-hand chords are also common to both). In the secondary theme, in addition to the lingering sound of G major through secondary dominant chords, the transition to the closing section begins without the theme being concluded by a definitive B-flat major perfect cadence, thus lacking thematic stability in both harmony and melody. Thereafter, the tonality remains unstable until the end of the closing section, despite the insertion of a B-flat major full cadence midway.

Development

The development section begins not in G minor, as might be expected from the last harmony of the exposition, but in C minor, with a chord on G serving as the dominant. The beginning of the development section presents a new chorale-like theme, followed by several sections based on triplet passages, material from the exposition, and the new theme from the development's opening. Immediately before the recapitulation, a portion of the second movement recurs, revealing Eberl's extraordinary stylistic characteristic here.

Recapitulation

In the recapitulation, in accordance with the tonic recapitulation of both themes, the modulatory section leading to the secondary theme in the exposition needs to be altered from that of the exposition. In this movement, after the recapitulation of the first 10 measures of the movement, Eberl repeats the chordal motive from measure 11 to adjust the tonal plan for conciseness, omitting almost the entire transition section. Thereafter, the recapitulation largely follows the standard form up to the middle of the closing section (measure 123 of the exposition). In the coda, the harmonic range is significantly expanded by bold modulations from C minor (flat-side) to E minor (sharp-side) utilizing enharmonic equivalents. Furthermore, after the tonic dominant chord, stable tonic G is repeatedly avoided through techniques such as inserting rests and reinterpreting a G major triad as the dominant of C major, which supports the expansion of the coda's scale. Its content is also rich and substantial, with extensive elaboration and modulation of the main theme.