The A-B-A ternary structure is the foundation and the most commonly seen structure in western music. It posits the general idea of “starting somewhere, going to another place, then coming back”. The structure is commonly used because it tends to remind people of certain situations that might come up in life – from home to work, back to home; leaving one’s town and out into the world, then coming back with a perspective renewed. The “A” section usually symbolizes some sort of attachment to something stable – one’s home, one’s individuality, one’s ideology – while the “B” section investigates its relationship to the idea of change.
As an improvisational exercise, what consists of “A” and what consists of “B” can be largely arbitrarily chosen, although it may gain more of a personal significance if the materials were selected according to the improviser’s background and tastes. This personalized approach may not be appropriate when playing within a group, so something more generalized may prove to be more effective in larger sessions. The selection could be something as simple as “A – short notes” and “B – long notes” or “A – loud” and “B – soft”; almost anything can be used as long as the materials are distinct enough from each other.
The important aspect of the exercise is to actually hear and feel the music modulate from one state to another in real time. The distinctions between A and B are made only to have the lines blurred through a greater understanding of causality. This is an experience which is very difficult to replicate with notated music or imitations of recordings, due to the fact that performers often focus on the individual notes so intensely that the perspective on the overarching structure becomes lost. Perceiving structure in notated music usually requires the performer to have an extensive knowledge of music theory, but these improvisational exercises allow the musician to establish an intimate relationship with the form much more quickly.
If the improviser so wishes, they may experiment with other variety of formal constructions – ABABA, ABCBA, rondo, ritornello, fugues, theme and variations, concertos (with cadenzas!), flow-charts, process forms, or whatever else may come to mind. (More of these will be added to the blog as time goes on.) These guidelines are good as solo exercises but it is recommended that it also be attempted in group sessions as well, as the dynamic is considerably different when the transitional speed from one section to the next becomes a matter of group consensus rather than individual judgment.
Here is one example of our group (The A-Tribute Ensemble) doing an session in ABA form. Melinda (violin) starts the A section with something melodic, then contrasts it with a chormatic B section, Chris (cello) uses the plucked sounds as his A and bowed sounds as his B. I (piano) decided to introduce a theme played in harmony in my A, then contrasted it with a B section that sound a lot more disjunct and angular.
Although we were all doing different things at the same time, since we largely moved from each section to the next as a group, it gave the session a level of coherence that everyone could hear. And when the group collectively goes back to the A, there's a feeling of relief and resolve -- as if returning to something familiar.