Commentators have sometimes remarked on similarities between contemporaneous piano sonatas and quartets by Beethoven, as if the composer were developing ideas at the keyboard before transferring them to other genres. A particularly close connection can be seen, however, between two works in B♭ major that are separated by a greater distance in time: the Piano Sonata in B♭, op. 106 (Hammerklavier) and the String Quartet in B♭, op. 130. Correspondences between the respective first movements are particularly strong, and they suggest that the sonata may have served as something of model for the quartet.
Yet the same elements that contribute to a highly integrated structure in the sonata seem to serve quite different purposes in a quartet characterized by a pointed disintegration of normative procedures. A comparison of the two works shows not only how Beethoven's style underwent significant change in the intervening time, but also how the quartet may serve as a critique of the sonata in an act of deliberate stylistic distancing. This brings into question the well established concept of a unified “late” or “third-period” style.