That shepard tone was extremely interesting. I never knew that there was a sound equivalent to optical illusions. You want to hear the note keep going down in pitch, but it never does. It's frustrating and interesting at the same time. It seemed to me that when the tone was getting lower, the starting tone would be added at a lower gain and would slowly increase in amplitude. Then the starting note would surpass the lowering note in amplitude and the cycle would start all over again. If you listened really closely you could hear where the cycle began and ended.

It's weird how filters actually take away from sounds rather than add to them. With all the effects that result from using these filters, one would expect that things are being added. When you take out certain frequencies and boost others, you can change the timbre and envelope of the sound. I wonder if you take out certain frequencies from the shepard tone, if it would be easier to decipher its audio illusion.