Ludwig van Beethoven's Diabelli Variations, Op. 120 was his greatest masterpiece for the piano, and its 33 variations on a simple waltz transcended the extraordinary keyboard works that preceded it, including his other sets of variations, bagatelles, and the 32 piano sonatas. Composed between 1819 and 1823, contemporaneously with the Missa Solemnis, it was published as the first volume of Anton Diabelli's Vaterländischer Künstlerverein. Diabelli had asked the leading composers of Europe to compose a single variation on his original theme, and he collected examples from Carl Czerny, Franz Schubert, Johann Nepomuk Hummel, Ignaz Moscheles, a young Franz Liszt, Franz Xaver Mozart, and Archduke Rudolf of Austria, among many others, but Beethoven's monumental contribution exceeded them all. The Diabelli Variations are regarded as a summation of Beethoven's methods of composition, and it requires an experienced pianist to communicate its myriad connections to all that went before, perhaps most significantly to the late piano sonatas, which it most closely resembles in tone, breadth, inventiveness, spiritual depth, and emotional impact. John O'Conor's 2016 release for Steinway & Sons offers a spontaneous and fluid performance that ranges in expression from humorous and mercurial in the early variations, to profound and awe-inspiring from the midpoint on, and he displays a fine balance between vigorous virtuosity and sublime restraint. Steinway & Sons provide clean and crisp sound, so all the details and nuances in O'Conor's sensitive playing are easily heard. Highly recommended, especially for fans of this amazing piece.