Measures 25-28a of Mozart's Piano Sonata in D, variation 12, are rife with tension and unusual, quick chord changes. In the key of D major, the chords progress like this:
I - viio/ii - ii - viio43/ii - ii6 - viio - I - viio43 - I6 - V65/IV - iv
The hurried resolutions occur within the space of quarter notes, not really allowing a solid cadential feel, until the arrival at the beginning of measure 28, on the mixture chord - G, Bb, D - minor four in D. Mozart sets up for the mixture chord by lulling us into a false sequential feel - viio/ii resolves to ii, then viio resolves to I. Next we hear the most stable sounding dominant functioning chord - V65/IV - and the listener thinks, "Oh, I'm finally coming home... predominant, dominant, tonic, here we go" - surprise! Mixture chord! Minor four! Where are we? Where are we going? Will it ever end? Can we escape all the tenseness? Not in this excerpt. Thus, Mozart proves once again that he still has a few tricks up his sleeve.
PS - as of Sunday Mozart was 252, by the way. Happy Birthday, Wolfie.