Before I point you at it: It works only with Internet Explorer with Java. That's what the site says, and it certainly doesn't work with Netscape/Mozilla/Firefox. I haven't checked with anything else.
The IBM Glass Engine enables deep navigation of the music of Philip Glass. Personal interests, associations, and impulses guide the listener through an expanding selection of over sixty Glass works.
It's pretty amazing. You can navigate by work title, composition date, track title and track length, and also by 'joy', 'sorrow', 'density', 'intensity' and 'velocity'. Just click-and-drag on a scale, and listen to what you find. By default, the Glass Engine uses the full database of works, but you can restrict it by genre, such as Film, Ballet or Opera. Not everything is in the database (nothing later than 1999, and it seems to be limited to pieces that have been released commercially, so there's nothing from The Making of the Representative from Planet 8, for example) but there's lots in there.
It helps to have a decent-speed 'net connexion, and the sound isn't CD quality, but it's good enough to explore and enjoy.
Now all that's needed is for people to implement this for all the other composers :)