The arioso leads into a three-voice fugue, whose subject is constructed from three parallel rising fourths. The opening theme of the first movement carried within it elements of this fugue subject (the motif A–D–B–E) and sees a foreshadowing of it also in the alto part of the first movement's antepenultimate bar. The countersubject moves by smaller intervals. Kinderman finds a parallel between this fugue and the "fughetta" of the composer's later "Diabelli Variations", also finding similarities with the "Agnus Dei" and "Dona Nobis Pacem" movements of the contemporaneous "Missa Solemnis" (sketches of this work and the "Missa Solemnis" are to be found interspersed in the same notebook) .