So we're getting into a module reorganization spree before hitting Alpha. Most music has been pulled out of the engine and the way we bundle modules with the game zip is changing. Right now the attached zip contains the usual module lineup (with some small changes - see forum for details) but the zip the Launcher gets you only contains the Core module. So if you go through the Launcher you won't get extra modules for a bit.
More related changes are coming and the Launcher should be tweaked to handle modules better soon, including more options.
See forum for news post: http://forum.terasology.org/threads/merry-xmas-and-all-the-other-things-new-stable-out.1180/