Tonal dynamics and metrical structures in jazz improvisation

In the statistical analyses reported in this study 17 bebop styled jazz improvisations were examined. The goal was to determine some of the ways that the musicians utilize in order to cope with the cognitive constraints of improvisation. In particular, the tonal, harmonic and metrical preferences of the improvisers were investigated. These results seem to suggest that at least in this type of music both global and local tonal orientation affect the process of improvisation, for the global tonality and certain important chords seem to serve cognitive reference points. Also various metrical structures were used to emphasize important tonal material or mark phrase boundaries. Moreover, it was found that the improvisers used patterns of tension and release in order to maintain both interest and coherence in the improvisation. The results give strong evidence that bebop styled jazz improvisation is at the same time remarkably structured and dynamic. It seems that the process of improvisation is to a considerable degree based on various interrelated hierarchical principles which help the musicians to maintain coherence and interest in their improvisations. Further they show that the human cognition is able to handle very sophisticated hierarchical structures while improvising music. It is also noteworthy that these principles are well in concordance with the empirical research on music cognition.