When you're playing music and movies in WMP 11, you can change the player's audio and video playback settings. These settings are generically referred to as enhancements, and you display them by clicking the down arrow on the Now Playing tab and selecting View Enhancements.
This opens the Enhancements pane at the bottom of the WMP window. You can cycle through the various enhancements by clicking the blue left and right arrows.
Probably the most useful audio enhancement is the graphic equalizer, shown in Figure 49. You can choose from various preset equalization settings, by clicking the Select Preset link; this displays a variety of common equalizations.