If you like to choose music to match your mood or perhaps pull you out of one, IBM has created an online tool that will be of interest. The tool called the Glass Engine allows users to surf a selection of Philip Glass works not only by standard categories like work title and year, but also by more subjective characteristics like joy, sorrow and density. If a selection is too soft, crank up the intensity. This is not an exercise in Artificial Intelligence: Glass\' longtime producer and sound designer, Kurt Munkacsi, has assigned values to the tracks. Some appear a bit conflicted, expressing high sorrow and joy simultaneously. -Brooke Singer