What holds the attention of two feisty teenagers who work with increasing delight on a Dvorak Slavonic Dance for piano four hands? What keeps it from becoming hopelessly boring even after months of slogging away at it?

I listen essentially out of curiosity to answer that question, as I would not have been capable of such sustained interest at their age. Today I could tell that it is not just the composition that holds their interest with its surprising variation of eight rhythm and tone events in every bar. It is also that they hear completely differently from one another and that they are mutually fascinated by the differences.

One, by nature a composer, responds to register changes in the bass as if orchestrating. He cannot simply play a bass line an octave lower because the sound is fundamentally different, almost to the point where he does not see how he can make so much happen with just one hand. His intuitive response to every nuance of color and resonance affects his sense of timing and challenges his sense of control. The two of them have been collaborating at the piano off and on for the past six years, learning to be flexible in every aspect of their playing. By now accustomed to one other's idiosyncracies, they are mature enough to get beneath the surface to the place where their subjective experience meets the composer's genius.

When their time is up I have to pry them off their chairs.

Surely this is a music teacher's best reward.