Check it out—an in-browser oscilloscope visualizing a few different songs using WebGL. The scope uses XY-mode, where the sample values of each stereo channel are mapped to each of the axes, instead of the X-axis representing time.
When you set up a scope this way, you can get some really interesting and unexpected patterns, such as Lissajous Figures. For instance, two sine waves of the same frequency and the same phase gives a straight line segment, but putting one of those sines 90º out of phase gives a perfect circle!
The songs used in the above visualizer take advantage of this by sneakily encoding all kinds of nifty shapes and patterns into the song itself, invisible until revealed with the XY oscilloscope.
The code that makes it happen is all right here (and using ECMAScript 6!).