Emergence of metrically structured rhythms and inter-partner coordination in joint drum improvization

Improvization is a common aspect of music across cultures and eras. Due to its spontaneous nature, it often proves difficult to examine empirically how collective improvization evolves, unless genre-specific constraints are available and followed by experts (e.g., jazz). Here, we investigate the rhythmic dimension of free improvization by non-experts. We focus on two widely used approaches in joint musical improvization: call-and-response (trading) and simultaneous playing (tandem). We hypothesized that non-experts could engage in meaningful joint music-making with a model partner, and that they produce rhythmic patterns with different emergent structures depending on the task. The first author served as a confederate playing with each participant for five blocks each of trading and tandem tasks. To preserve the open-ended nature of improvization, neither metronome nor background music were provided. Preliminary analysis of the rhythmic content indicates that within-player inter-onset-intervals (IOI) reflected a clear hierarchical metrical structure. Additional analysis suggests bi-directional influence between partners in terms of IOI distribution, note density, and timbre choice. During tandem improvization, each partner favored timbres the other did not, showing a complementary pattern. During trading, timbre choice appears more imitative. Subjects also reported an increase in their self-assessed competence and enjoyment of the task over successive blocks.