  We present and evaluate a novel interface for tracking ensemble performances
on touch-screens. The system uses a Random Forest classifier to extract
touch-screen gestures and transition matrix statistics. It analyses the
resulting gesture-state sequences across an ensemble of performers. A series of
specially designed iPad apps respond to this real-time analysis of free-form
gestural performances with calculated modifications to their musical
interfaces. We describe our system and evaluate it through cross-validation and
profiling as well as concert experience.
