The rainbow pendulum is a mathematical and musical wonder. There are 28 concentric semicircles with a moving dot on each one. The dots move back and forth at a constant speed, but not the same speed on different lines. When a dot hits the bottom of the screen, it produces a note and then moves back. This produces a beautiful musical scale- like effect. There is a curve made out of the dots that will first hit the bottom in one place, then two, then three, etc. After a while, dots on different lines line up for a few seconds, but when this happens, all of the dots are lined up with each other. The rates at which they move are an exponential function, with trigonometry involved somehow. It sounds wonderful, with overlapping scales combining and dividing, eventually coming back to one note.