Sound draws a spiral. If you start from C, and go up the stairway of notes to D, E, F, and so on, you’ll get to another C, which is not the same place you previously were but one floor up from where you started. Since the ratio of frequencies of two notes an octave apart is 2:1, going up one floor means doubling the frequency.
So what if this relationship were literally visualized in 3D animation? The result did not turn out very simple and clear since even a single note of an instrument contains multiple frequencies as its component. But at least it’s somewhat fun to watch, isn’t it?
Clicking on the demo below starts/stops the sound. Watch out for the volume on your PC.
Sound.comuteSpectrum() method, which is used to analyze the sound, seems to have several problems. One of them that is critical is that the method doesn’t work properly when more than two movies play sound simultaneously in FireFox. If you don’t see the demo, try closing other browser windows.
Another demo that works without music is also posted to wonderfl.