A Reuben’s tube is an apparatus used to demonstrate standing waves in physics; it’s akin to the gas lighter in your fireplace, but with sound added. At certain frequencies, the flames will vary according to the standing wave produced in the tube.

Things get exponentially more awesome if you make a 2-D tube, and apply more interesting music. At the link, the vid is cued to the music, but it’s really worth watching the whole thing.