"Skill development depends on how repetition is organized. This is why music, as in sports, the length of a practice session must be carefully judged: the number of times one repeats a piece can be no more than the individual’s attention span at a given stage. As skill expands, the capacity to sustain repetition increases. In music this is the so-called Isaac Stern rule, the great violinist declaring that the better your technique, the longer you can rehearse without becoming bored. There are “Eureka!” moments that turn the lock in a practice that has jammed, but they are embedded in routine.
As a person develops skill, the contents of what he or she repeats change. This seems obvious: in sports, repeating a tennis serve again and again, the player learns to aim the ball different ways…."
