Sonate für Pianoforte Nr. 12 in A-flat major, Op. 26 by Ludwig van Beethoven: Another less immediate connection exists with the main theme, also in A♭ major, of the Adagio movement in Schubert's piano sonata in C minor, D. 958. Indeed, Schubert may have borrowed these themes from Beethoven, as he often did in his compositions.