PWGL is a free cross-platform visual language based on Common Lisp, CLOS and OpenGL, specialized in computer aided composition and sound synthesis. It integrates several programming paradigms (functional, object-oriented, constraint-based) with high-level visual representation of data and it can be used to solve a wide range of musical problems.

The constraint package is a constraint satisfaction problem solver written in 100% pure Python. The implementation uses constraint propagation algorithms. Constraints and Domain implementations are provided to work with finite domains and finite intervals. It should be fairly easy to add new kind of domains such as finite integer domains, together with specialized constraints.