 11, 16, 22, and 27, the themes are less marked, and the overall effect is of homogeneity.As Mozart's art progressed, these themes sometimes become less strophic in nature, i.e., he binds them together into a more unified whole.In addition to the ritornello thematic material, Mozart's mature concertos nearly all introduce new thematic material in the piano exposition, the exceptions being K. 488 in A major, which, however, follows an unusual course after this, and K. 537.