Combined perception and control for timing in robotic music performances

Interaction with human musicians is a challenging task for robots as it involves online perception and precise synchronization. In this paper, we present a consistent and theoretically sound framework for combining perception and control for accurate musical timing. For the perception, we develop a hierarchical hidden Markov model that combines event detection and tempo tracking. The robot performance is formulated as a linear quadratic control problem that is able to generate a surprisingly complex timing behavior in adapting the tempo. We provide results with both simulated and real data. In our experiments, a simple Lego robot percussionist accompanied the music by detecting the tempo and position of clave patterns in the polyphonic music. The robot successfully synchronized itself with the music by quickly adapting to the changes in the tempo.