Techniques to Foster Drum Machine Expressivity

Electronic drum machines need algorithms to help them produce \expressivesounding" rhythmic phrases. In [Bilmes, 1992], I claim that three perceptually separate elements characterize percussive rhythm: metric content, tempo variation, and deviations (formerly called event-shifts). Herein, I demonstrate that algorithms based on this model may considerably facilitate reproduction of expressive rhythm. I describe one such algorithm which extracts the separate elements from a percussive performance. The performance is then resynthesized with varying degrees of tempo variation and deviations. Without the deviations, the performance sounds mechanical. With them it sounds rich and alive. Consequently, I claim that we should begin a concentrated study on the separate elements characterizing percussive rhythm, particularly deviations. To this e ect, development has begun on a graphical drum machine program with which deviations may be explored.