Today, contemplating Mozart's only piano sonata in G major with a longtime dedicated amateur student we hit on Mozart's trademark combination of the strong with the weak. Sound the stronger two notes of any triad, then add in an unlikely third note, transforming the expectation of strong into vulnerable. Put a full triad in root position on the downbeat opening a section: it will be strong, no? Well, not if it's in the wrong key and minor instead of the expected major.

Such elements are the stuff of high artistry. They are instinctively felt and reacted to by the musical amateur and by the child who feels free to manifest a reaction. The reaction usually show up in "wrong" notes--errors that reveal the activity of the inner musical sense at work.