RTS: Real time scheduling in common music

RTS is a real time scheduler for the Common Music algorithmic composition system. RTS enables compositional algorithms written in Lisp to generate sound in real time and to communicate with concurrently executing applications via OSC [1], Portmidi [2] and Midishare [3] connections. One of the nicest features of the RTS scheduler is that it can be "invisible" to musical algorithms, that is, a given musical algorithm is able to execute in either real time or non-real time modes without any change to its code. This allows a composer to use the identical suite of algorithms for both file-based and interactive work simply by switching scheduling modes, without having to change how the algorithms themselves are expressed. Of course real-time execution can limit how much computation can happen in a given execution slice and so the RTS system also provides a library of compositional tools specifically designed with real time execution in mind for composers that want to optimize their algorithms for real time use. The RTS scheduler is based on POSIX threads [4] and is implemented as an optional software system that can be loaded into Common Music on demand, whenever the composer wants to work in real time. RTS can run in any Common Lisp or Scheme that supports callbacks and foreign function calling. The current bindings support OpenMCL [5], SBCL [6] and Gauche Scheme [7] on both Linux and OS X. A version may be available for SBCL/Windows in the future.