Commentaries
Since the work was first published, commentators have tried to find patterns, even an overall plan or structure for this huge, diverse work, but little consensus has been reached. Several early writers sought to discover clear parallels with Johann Sebastian Bach's Goldberg Variations, without great success. Others claimed to have found symmetries, three groups of nine, for example, although the penultimate Fugue had to be counted as five. The work has been analyzed in terms of sonata form, complete with separate 'movements.' What is not disputed, however, is that the work begins with a simple, rather commonplace musical idea, transforms it in many radical ways, and ends with a sequence of variations that are cathartic in the manner of other late Beethoven works.
Read more about this topic: Diabelli Variations