GamesRadar: What is Portal 2’s adaptive music system? How does it affect the experience?
Mike Morasky: We developed a brand new system that is used to handle all dynamic audio in Portal 2. As the system is very open and easy to customize, the types of musical interactivity we developed are widely varied and generally designed for the specific gameplay at hand. Overall the interactive musical experience tends to become one of exploration, as if the music is emanating from the facility and devices of Aperture Science itself, often giving the player total control over how much or little they want to expand that aspect of the experience.
It makes for interesting reading/listening, and illuminates another aspect of the game that hadn't really been talked about until this point. You can read the entire interview at the GamesRadar site.