The exact date of composition is unknown, but sketch studies suggest that No. 1 was composed during the Bonn period and revised in Vienna. This work adopts an unusual four-movement structure for a piano trio of its time, and perhaps as a manifestation of the composer's pride, it was given the opus number 1 anew, separate from WoO 40, which was already designated as Op. 1, and advertised as “Grand Trio.” The dedication was not to his teacher Haydn but to Lichnowsky, which reveals the composer's unconventional character.

First Movement

The first movement is in sonata form. In the main theme, the staccato and ascending arpeggios of the preceding phrase are balanced by the slurred descending melody of the subsequent phrase. The opening of the subordinate theme group is a homophonic phrase reminiscent of the chord progression in the main theme's preceding phrase. The violin's eighth-note rhythm, which ornaments the chord progression in the repetition, creates a natural connection with the subsequent sections.

In the development section, material from the exposition is utilized in sequence: the arpeggiated motive of the main theme, the two-measure melodic figure with an ascending scale from the latter half of the subordinate theme, and the stepwise motion of the codetta.

In the recapitulation, changes in harmony and rhythm (measures 205, 213-214, 228) seem to reduce stability compared to the exposition, serving as a driving force towards the extensive coda. In the coda, the material is processed to an extent comparable to the development section, including modulations using the opening phrase of the subordinate theme group, which had not appeared in the development, and the most urgent responses of the arpeggiated motive within the movement.

Second Movement

In the second movement, a rondo, the independence of the string instruments, especially the cello, is noteworthy. Indeed, the piano's dominance, as it carries most of the variations and ornamental figures of the recurring theme, is still high. However, in the first episode, the string instruments echo the melody over the piano accompaniment, and in the second episode, where modulations are concentrated, the key shifts as the three instruments alternate the main melodic voice. Furthermore, in the coda, each instrument has ample melodic interest, with the cello, for instance, introducing fragments of the theme.

Third Movement

The third movement contrasts a lively scherzo, where the opening embellishing figure dominates the entire section, with a trio where the piano moves smoothly over string chords. A phrase of the same type as the scherzo's opening, where the initial motto motive is followed by stepwise motion of long note values counted as one beat per measure, also appears in the third movement of Op. 4, a work similarly revised from the Bonn period. In the scherzo, the beginning and ending measures of many adjacent sections overlap, allowing the music to flow seamlessly as it transforms freely from one idea to the next. Furthermore, the chromatic progression at the beginning of the movement, which blurs the movement's tonality, and the fact that the violin's true theme presentation is delayed by four measures after what appears to be a three-voice imitation at the beginning of the middle section, likely contribute to the movement's whimsical character.

Fourth Movement

The final movement is full of dynamism, with elements such as the opening leaping figure, the two-note motive connecting weak and strong beats in the transition (m. 38ff.), the continuous turns and embellishing figures (m. 94ff., m. 104ff.), and the descending second from an appoggiatura in the codetta, all generating propulsive energy.

The development section begins in the relative key of the dominant, and after presenting material from the exposition such as the opening theme, the closing theme, and a descending scale utilizing the rhythm of the transition, the latter half features chromatic string progressions and continuous piano arpeggios, finally extending the dominant chord of the tonic to prepare for the recapitulation.

In the recapitulation, the arpeggiated motive at the end of the subordinate theme undergoes rhythmic diminution, leading into the coda. Following a series of leaping motives, modulations occur based on the subordinate theme's phrase, which, as in the first movement, had not appeared in the development. Subsequently, after the latter half of the development, the closing theme, and its variations, the leaping motive returns, and the movement concludes with repeated tonic cadences. The coda possesses a richer content than the development section in terms of its length, diversity of material, and striking modulations between E major and E-flat major via chromaticism.