Description:A loudspeaker in one end of a four-inch diameter galvanized iron tube creates standing waves in propane gas in the tube. The gas emerges out of a series of small holes in the top of the tube, forming a long line of flames when lit. Any sound resonant with the length of the tube can create standing waves in the gas which are readily visible as a pattern in the height of the flames. Both rhythm and frequency response can be seen nicely in music. An oscillator and a cassette deck are provided with the demonstration to be used as simple sources for the loudspeaker. Or, a voice or other music or audio can introduced using a microphone and amplifier or external input jacks, available upon request.