Abstract: This work describes a computer system for authoring dance shows. The system can be used both as a mechanism to synthesize virtual group performances and as a tool for interactive design and visualization of real choreographies. To this end, we use motion capture of dance sequences that are synchronized with an underlying musical composition as input. We adapt motion synthesis methods for use in combination with a musical track. The authoring system provides methods for controlling group movement of dancers on stage, such as creating formations and following trajectories. Our integrated platform supports collaboration among artists, allowing the show to naturally evolve from iterative contributions from dancers, musicians, and choreographers.