It is known as the "Gassenhauer (=popular song) Trio" because its final movement features a variation movement based on a theme from Joseph Weigl*1's opera, L'amor marinaro, which was very popular at the time. This is the only multi-movement work by Beethoven that uses a theme by another composer. There are various theories regarding the choice of the variation theme, including the clarinetist's request, but an anecdote suggests that the composer himself was dissatisfied with the theme by another composer and even considered rewriting the final movement.

The work as a whole centers on imitation and dialogue among the three parts. The piano part envelops the main melodies played by the other parts with arpeggiated chords and high-pitched ornamental figures, enriching the overall sound.

In the first movement, which is in sonata form, the three-note motive of the opening theme and syncopated rhythms are developed. Furthermore, the abrupt modulations just before the secondary theme and at the beginning of the development section add novelty. The piano arpeggios in the development section might have been played throughout with the pedal held down, given the lighter sound of Viennese pianos of that era.

The slow movement is in ABA' three-part form. In A', the piano's ornamental figures should not overshadow the main melody.

The final movement shows ingenuity in the arrangement of variations:

• Variations 1-2 are paired by the presence or absence of the piano.
• Variations 4-5 are paired by their half-note rhythm.
• Variations 7-8 are paired by the commonality of the clarinet and cello's dialogue and the piano's chord progression.

The final variation features a trill lasting for 15 measures, elaborately decorating the theme.

The violin part, published at the time of the first edition as an alternative to the clarinet and attributed to the composer himself, shows consideration for string instrument idiom in places, such as the use of double stops.

*1 Joseph Weigl (1766–1846)

A composer and conductor active in Vienna. From 1791, he succeeded Salieri as Kapellmeister of the Imperial Court Theatre in Vienna. He left many achievements in the field of opera.