Both of these are Liquid Light, playing to the same music. One of them is listening to it, and the other is not.
Watch for 10 seconds, then pick the one that is listening, or say you can't tell. There are five rounds.
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My 1998 patent (US 6,163,323) rests on the idea that images and colors changing on many independent random clocks look as if they keep time with any music, even when nothing is listening.