Crank up your music and watch them penguins dance! Tap manually along with the beat to adjust the dancing speed. Change the emotion level, and make them freak out! Note that automatic beat detection is sampling audio from the input device you choose in the drop down menu. Your microphone should be fine for music playing out loud. If you want dance dance! to internally sync with music from another application, a free utility such as Soundflower can be used to reroute the system audio.