Oh, I should have said, the IR sensor should ideally be in line of sight of the dudder, but they can work using reflected light. Having the LEDs set on red seem to reduce the effectiveness of the dudder ... I guess because that colour contains more IR than the other colours.
I'll not go down the music route ... can't imagine it would produce much of an effect driven by Radio 4! But if you want to fit that, it looks like it would replace the white controller in the description above.