^Yup. It just sounds like 3 octaves of the same note going up chromatically. When it gets to the end and you replay, your brain expects the next note in the chromatic scale, and that's the one it chooses to hear.
That was actually interesting. Probably chords that cover many octaves so your mind begins selecting them individually and it gives that illusion.
Yeah I know right! I was like, I hope people don't just judge it by the way it looks, cause it looks retarded, but if you try it, it's actually pretty neat! [:)]
I know this thread was mostly about the audio illusion itself, but I might as well show something that I think anyone who appreciated that video would also find interesting.
This is Bobby McFerrin, one of the world's best vocalists, showing the "expectations" of the mind through sound and the pentatonic scale. Definitely worth a watch.