How is a Classical piano sonata like a computer game? you might well ask. Let's say you have a harpsichord. It has black keys and white keys and they produce similar tone color. Now suddenly here's a keyboard on which the white and black keys produce entirely distinct tone colors. Wouldn't you be tempted to explore set-ups in which this dichotomy would prove amusing? or threatening? or _____ (fill in the blank)? The possibilities are endless.

Let's take an actual scenario: Two white keys, a descending minor third. Wait a minute: don't we orient to intervals rising rather than falling? Where are these tones headed: down another third--in which case will it be major or minor, white key or black key? Or down a fourth, white or black key?

Let's say the composer gives us a major third onto a white key. Aha! It's major. But he slides off in a slightly complicated manner slurring over the barline onto the fourth, a black key. Uhoh.

We thought we knew where we were. But that pesky black key presents a dilemma--auditory, not visual. For the eye can see that the accompanying Alberti bass figure places the black key within the dominant harmony. Even so it sticks out, doesn't it? whether we want it to or not. Herein is the enticement to pursue the matter--the plot, if you will, through three movements. It will occupy you for at least 15 minutes--perhaps even a lifetime. (Mozart K. 283)