In classical sonata movements in the major mode the tonal motion of the development section is most often directed back to the dominant, which is then extended for several measures until the return to the tonic. However, in several Mozart works the goal of this motion is not the dominant, but the major triad on the mediant (III#); from there the return to the tonic is accomplished either directly or through the dominant, which is sometimes passing but other times more extended.1 The greater the emphasis on the connecting dominant the more obvious it is that the motion to the mediant is subsidiary to the larger prolongation of the structural dominant. However, when the connecting dominant is only passing or missing entirely, the mediant appears to divide the tonal space between the preceding dominant (end of exposition) and the subsequent tonic. Thus, in these circumstances, the return to the tonic is accomplished by a large-scale bass arpeggiation of the tonic triad, the members of which support the harmonic progression V-III#-I.2 The following study will focus on those movements where this large-scale bass arpeggiation is most clearly articulated. These are the first and third movements of the Piano Sonata in F, K. 280, and the first movements of the Sonata in F, K. 332, and the Sonata in Bb, K. 333. In each case it will be shown how this pattern and its elaboration is