Have you ever been to a recital where a student, usually a younger student, makes a mistake, backs up slightly and makes the same mistake again? Often at that point, they get stuck in a sad cycle of mistake, repeat, mistake.
What is going on is not that the student hasn’t practiced at all. It’s that they haven’t practiced for continuity across a difficult spot. This is what is know as the continuity rule. To illustrate the continuity rule, let’s take a passage from the D major Prelude in the Well-Tempered Clavier, Book 1 by J.S. Bach.
At tempo, measures 15-17 require very specific fingerings and can easily trip-up the performer. If we were practicing this with the continuity rule in mind, my first pass would look like this:
So in my first pass, I’m playing the 16th notes in each beat as a group, but continuing into the next beat. Therefore, I’m landing on the next beat - playing 5 notes in other words. In the second pass, I can extend this in several ways. One way is to take two beats at a time:
In this second pass, I play the 16ths in the first and second beats as a group, landing on the first 16th of the third beat, and so on. Since this is in common time, I can just keep doubling the unit length for practice, or I can just add one unit (4 sixteenth notes) at a time. I call this whole process “practice for rhythmic continuity.” As the technical problems begin to dissipate, we can turn to integrating it into the whole of the piece, backing up before the challenging section and stopping sometime after that section. I’ll call this “practicing for musical continuity.”