Open Sound World, or OSW, is a scalable, extensible programming environment that allows musicians, sound designers and researchers to process sound in response to expressive real-time control. OSW combines a familiar visual patching paradigm with solid programming-language features such as a strong type system and hierarchical name spaces. OSW also includes an intuitive model for specifying new components using a graphical interface and high-level C++ expressions, making it easy to develop and share new music and signal-processing algorithms.