E-flat major, 3/4 time.

The bass part forms a basso ostinato (ground bass), repeating a fixed melodic pattern, reminiscent of a trio sonata consisting of two principal voices (obbligato) and a basso continuo. At first glance, the two principal voices appear to play freely over a constant harmonic support, but the middle voice imitates the upper voice, revealing that it is written with extensive use of counterpoint.

The entire piece is structured in two well-balanced sections, with the second half beginning at measure 17.