I expect that all of us have found from our own performance and from directing our performance ensembles that transitions always need extra practice; those measures in a musical work where the composer moves from one section to the next, or one theme to the next. Everything is going well, and then we arrive at something different and there is that hesitation when we can’t quite keep the music going. So we practice that transition over and over until we can play or sing through it smoothly and seamlessly. Why are musical transitions so difficult? What is going on in our brain that suddenly makes it so hard to go on and continue to play correctly?

Musical perception is a lot like visual perception. We organize what we hear into groups that consist of things that our brains perceive belong together. Examples of rules by which our brain organizes music include close pitch proximity, continuance of the same articulation, dynamic, or rhythm pattern, similar or same timbres, and organizing a group of notes the same as a parallel group we have already heard. In between these groups, there are boundaries. Boundaries can be rests, relatively long durations, or a highly stable chord, among others.

The difficulty in transitions is that they occur at a boundary. At that point we are trying to force two groups together that our brain has decided belong separated. There is momentary conflict between what we want to do and what our brain has prepared us to do. That is why we can play or sing after the transition and before the transition, but not through the transition. Our brain is happy to keep the two groups separate, because that is how it has represented the music in memory. We want to go, our brain wants to pause. Fortunately, musical structure as it is understood by the human brain is hierarchical. That means that those two groups we are trying to put together are two halves of, and subordinate to, a larger group comprised of the two subordinate halves. By widening our view and thinking of the two groups as one, we can change the way our brain describes the transition to our consciousness. This takes some analysis during which the musician finds a stronger boundary at the end of the two smaller groups, and that stronger boundary then becomes the end-point of the group. This larger group then can likewise be thought of as half of a still larger group. The process theoretically continues on to the end of the work or movement, although most of us will find it too difficult to maintain a single group over such a long time span. The larger the group, the more difficult keeping it mentally intact becomes, but even succeeding at two or three of these transitions by understanding the music’s hierarchy at a deeper level is helpful in that it eliminates one or two troublesome transitions.

Now, let’s briefly see how this works. Here is the opening of Mozart’s Sonata in C major, K. 545.

I can easily perceive each measure as a group. The first measure is all C major, the second measure starts on a dominant chord, then returns to the tonic, and there is a relatively large leap between the G an the B in the melody, suggesting a group boundary. The next two measures are parallel to the first, and so also can be divided into two groups, one for each measure. With the melodic leap and the bass note change, going from one measure to the next can easily feel like a transition. But the third beat of the second measure is much more stable than the fourth beat of the first measure, and the second measure ends with a rest, which is a much stronger group boundary. Together, the first two measures make a complete sub phrase, and so makes a stronger group than the one measure arrangement. Now, with the goal of the full cadence on beat three (and four) of the second measure, I can more easily connect the two measures. Likewise with the third and fourth measures; measures 5-8 look like they could each be a group, but there is a descending progression that doesn’t conclude until the end of measure eight, where there is an elision that both completes the melodic descent to D and begins the cadential sequence that brings the piece to a half cadence in measure 12. At this point, we find that the first 12 measures are one group, made of three subordinate groups of four measures each, which are each made of two subordinate groups of two measures, which are made of two subordinate groups of one measure, taking us back to where we started, confronted with the urge to pause at the end of each measure. By seeing the larger groups, and thereby organizing the music in such a way that it has fewer group boundaries and therefore transitions, we have an easier time keeping the music going. Our technique is urged forward by our structural understanding and audiation of the work.