I could watch and listen to this all day long The "this" in question is the Whitney Music Box, "a musical realization of the motion graphics of john whitney as described in his book 'digital harmony'." According to the site:
in three minutes, the largest dot will travel around the circle once, the next largest dot will travel around the circle twice, the next largest dot three times, and so on.
the dots are arranged to trigger notes on a chromatic scale when they pass the line
Hat tip to Randy McRoberts for the link. And thanks to KrazyDad, who writes more about Whitney's pioneering work in motion animation and computer graphics.