He began work on the second sonata of Op. 102 shortly after the first (both were completed by the autumn of 1815). It has the most conventional form of all the sonatas, comprising three movements with, for the first time, a slow middle movement. The opening Allegro con brio begins with one of the most immediately accessible and memorable themes in all Beethoven's chamber music, followed by a more lyrical theme. The life-affirming energy of this first subject, which dominates the development section, could not be more strongly contrasted with what follows in the second movement, which opens with sombre, almost funereal lament in D minor, shared in solemn dialogue between the two instruments. A gently flowing section in D major offers some respite before descending back to the minor, though the movement finishes with a hushed passage that explores completely unexpected tonal territory, from D minor to C sharp minor and back again, before leaving the listener hanging on a dominant chord. And even once the third movement begins, we're still left hanging, as the cello and piano tease with ascending scalic passages. It is only when the third of these phrases (in the cello) morphs into a fugal subject that the resolution is finally granted. Despite the traditional structure of the sonata, Beethoven once again defies convention by making this finale a four-part fugue rather than the expected rondo, and seen from the perspective of his entire oeuvre, this might be considered a forerunner to several other fugal movements that permeate his late works, most notably the finale of the Piano Sonata Op. 106 'Hammerklavier' and the epic Grosse Fuge, Op. 133 for string quartet. In this contrapuntal writing we can clearly observe Beethoven's preoccupation with Bach, which greatly increased around the time of the sonata's composition, although he had venerated Bach's music ever since his youth (a fact that lends further weight to the claim that the aforementioned reference to the Es ist Vollbracht aria in the Op. 69 sonata was not accidental).