This is the only sonata for two pianos completed by Mozart. Its composition is believed to have taken place around November 1781, possibly in Vienna. According to a letter to his father Leopold, the work was apparently composed for performance with a pupil. It consists of three movements.

First Movement (Allegro con spirito)

This movement is in sonata form and in 4/4 time. The first theme in the exposition begins powerfully with a forte unison characterized by a march-like dotted rhythm. This is a typical gesture found in symphonies of the period. The second theme in A major is dolce and introduced by the second piano, but the first piano soon joins, forming a short canon.

After the exposition concludes with arpeggios, the development section introduces a new theme based on the same melodic pattern of descending then ascending motion, common to both themes of the exposition. Here, the chromatic movement of the motives evokes an uneasy emotion. Furthermore, the canonic treatment observed in the second theme is also present at the beginning of the development section. After intense unisons and increasingly vigorous interplay, the music transitions to the recapitulation. The movement concludes in a manner unusual for Mozart's works, by utilizing a theme from the development section.

Second Movement (Andante)

This is a lyrical movement in sonata form and in 3/4 time. This is the only movement in G major. The first and second pianos show variations such as taking over each other's roles or exchanging them.

Third Movement (Molto Allegro)

This movement is in rondo form and in 2/4 time. The rondo theme resembles his famous Turkish March. The keys shift variously, including A minor, A major, G major, and D minor, before returning to the tonic. The movement concludes brilliantly with a long coda.

This piece was composed in 1781, when Mozart was 25 years old. It was intended for performance with his talented pupil, Josepha Barbara Auernhammer. Mozart played the second piano (hereinafter referred to as 'secondo'), and Auernhammer played the first piano (hereinafter referred to as 'primo').

The work consists of three movements. A characteristic feature is the frequent alternation or responsiveness between the primo and secondo, often playing the same melody.

First Movement

Allegro con spirito, Sonata Form

The movement begins with a powerful and brilliant opening. The first theme features a unison movement in both parts, though in different registers. The light and vibrant rhythm is characteristic of Mozart. Both parts respond to each other, progressing without interruption. It is important to play the eighth-note figures precisely without breaking their continuity. The music flows continuously, with primo and secondo exchanging roles; it is crucial to maintain the flow by ensuring timely transitions for each figure.

The second theme, in contrast to the first, is played dolce. Although no dynamic marking is given, p is implied. Quarter rests appear every two measures, but one should conceive of a long phrase without interrupting the flow there. The second theme further develops, with both parts moving polyphonically in different registers. In the subsequent episode (transition section), the movements of both parts build up through alternating imitation. From measure 65, the primo sings the subsidiary theme before the codetta, concluding the exposition with the appearance of scale-like movements and arpeggios. Here, devise fingerings to maintain the unbroken unison movement in both parts.

The development section (m. 81~) begins with the secondo and transitions to the primo. A new melody develops for a while. It then leads to the recapitulation via a sustained A in the bass. The second theme is in D major. Before the Coda, the new melody from the beginning of the development reappears in the primo, develops, and then concludes.

Second Movement

Andante A (1-12) B (13-35) C (36-48) D (49-70) A (71-82) B (83-105) Coda (106-)

In the A section (exposition), the primo sings a gentle and quiet song (melody) accompanied by the secondo. Subsequently, from measure 13, the primo shifts its movement by one measure, which the secondo imitates, and they develop alternately while changing figures. Both parts should play while carefully listening to the volume balance between the melody and the accompaniment. In the D section after the repeat sign, a new figure appears. The movement in thirds is characteristic of Mozart; listen carefully to its sonority. Next, the primo sings the melody in double thirds with both hands. From measure 64, observe closely the movement of the primo's lower voice and the secondo's upper voice. Although both are sixteenth-note movements, they maintain a third interval while leading to the recapitulation. Listen carefully to each other and align movements: the secondo's bass provides the pulse with eighth notes, while the primo sings the melody freely, both attentively listening to each other.

From the A section recapitulation at measure 71 to the Coda, the overall movement is largely similar to the exposition. The third beat of the measure before the Coda (m. 106) would normally be F# leading to a G for a perfect cadence, but by using the altered note F♮, it briefly modulates to A minor, creating a lingering musical effect. The diminished seventh chord at measure 109 also creates tension, tightening briefly before the parts gradually weave beautiful melodic lines, leading to the conclusion. Perform while fully realizing the role of each part's notes.

Third Movement

Allegro molto, Rondo Form A (1-41) B (42-84) C (85-138) A (138-159) D (159-230) B (231-277) C (278-345) A (345-360) Coda (361-). The movement is broadly divided into 8 sections, concluding with the Coda.

A: The first theme, beginning with an anacrusis, starts in the primo. It has a vibrant movement. The phrase, which repeats and strings together the motif Mi-Re-Do#-Re-La, is similar to Mozart's Piano Sonata "Turkish March". After the repeat sign, the arpeggiated unison passages in both parts during the episode should be played with attention to balance. Subsequently, the secondo's sixteenth notes should be played legato and evenly as indicated, while the primo's rhythmic unison melody above it emphasizes the importance of their ensemble.

B: The beautiful melody of the primo's second theme in A minor should be played along with the secondo's chord progression. Roles exchange midway, but listen carefully to the transitions and the balance between the parts.

C: In the parallel major, A major, a chorale-like melody is created with soft chords. The long episode from measure 100 involves imitation and exchange of musical figures, but timing is crucial for the one-measure exchanges to flow smoothly without interruption. From measure 121, the primo has double-note movements with horn fifths, so listen carefully to the sound of the perfect fifths. Maintaining a variation of the first theme's figure from the beginning of the piece, it leads to a fermata. Here, it is recommended not just to sustain the note, but to slightly incorporate an arbitrary movement (like a cadenza) as a transition to A.

A: From measure 138, the first theme begins, and in D (m. 159~), a new melody appears. First, the primo plays for 8 measures in G major, followed by the secondo imitating the same melody. Then, the primo again plays a melody with trills. The left-hand arpeggiated accompaniment figure at this point descends measure by measure, which some may find slightly difficult to play. This part is eventually taken over by the secondo. This section can be considered a showcase for both parts.

B: From measure 231 in D minor, C: from measure 278 in D major, then A: from measure 345, returning to the theme, followed by a long Coda, concluding brilliantly and vibrantly.

Throughout the third movement, except for the solo in section D, both parts constantly have musical movement. Therefore, it is recommended to perform while considering the expression and balance of sound in each part's contribution, bringing out the unique charm of a two-piano performance.