Timings and interactions of skilled musicians.

We report here a preliminary study of interactive behavior between two members of a skilled string quartet performing a selected musical passage that required both performers to play several hundred notes in rapid succession at a steady tempo and in synchrony. Bowing movements were recorded using angular velocity sensors attached to their right forearms. The results show a high degree of temporal precision in both players. In addition, both players exhibited embedded rhythmic components in their timekeeping pattern, which arose from the grouping of notes in the musical score: four 16th notes to a beat. Within each group of four notes, we found a consistent timing microstructure: alternate upbows and alternate downbows had different mean durations. Both players' bowings could be modeled as alternating renewal processes. In addition, we report evidence of interactive coupling between the players as an essential component of their joint performance. The alternating renewal model enables us to propose a note-generation process that has implications for the central generators underlying the observed behavior and their hierarchical organization. We discuss the implications of this model for the organization and execution of more complex motor sequences.